Quarterly report pursuant to Section 13 or 15(d)

Fair Value Measures (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details)

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Fair Value Measures (Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($)
$ in Thousands
Sep. 30, 2020
Dec. 31, 2019
Sep. 30, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value $ 84,421 $ 391,233 $ 110,598
Total liabilities measured at fair value 3,601 3,034 630
Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 74,027 304,558 87,308
Total liabilities measured at fair value 0 0 0
Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 10,394 86,675 23,290
Total liabilities measured at fair value 3,601 3,034 630
Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Total liabilities measured at fair value 0 0 0
Accrued Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 2,415 2,266 521
Accrued Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 0 0 0
Accrued Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 2,415 2,266 521
Accrued Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 0 0 0
Other Long Term Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 1,186 768 109
Other Long Term Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 0 0 0
Other Long Term Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 1,186 768 109
Other Long Term Liabilities [Member] | Derivative Financial Instruments, Liabilities [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total liabilities measured at fair value 0 0 0
Cash Equivalents [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 56,337    
Cash Equivalents [Member] | Money Market Funds [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 56,337    
Cash Equivalents [Member] | Money Market Funds [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0    
Cash Equivalents [Member] | Money Market Funds [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0    
Cash Equivalents [Member] | US Treasury Securities [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   34,928  
Cash Equivalents [Member] | US Treasury Securities [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0  
Cash Equivalents [Member] | US Treasury Securities [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   34,928  
Cash Equivalents [Member] | US Treasury Securities [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0  
Cash Equivalents [Member] | Commercial Paper [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   33,587  
Cash Equivalents [Member] | Commercial Paper [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0  
Cash Equivalents [Member] | Commercial Paper [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   33,587  
Cash Equivalents [Member] | Commercial Paper [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0  
Cash and Cash Equivalents [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   288,926 72,941
Cash and Cash Equivalents [Member] | Money Market Funds [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   288,926 72,941
Cash and Cash Equivalents [Member] | Money Market Funds [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 0
Cash and Cash Equivalents [Member] | Money Market Funds [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value   0 0
Short-term Investments [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 70    
Short-term Investments [Member] | Money Market Funds [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 70    
Short-term Investments [Member] | Money Market Funds [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0    
Short-term Investments [Member] | Money Market Funds [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0    
Short-term Investments [Member] | Mutual Fund [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 1,025 1,668 1,477
Short-term Investments [Member] | Mutual Fund [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 1,025 1,668 1,477
Short-term Investments [Member] | Mutual Fund [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Short-term Investments [Member] | Mutual Fund [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Other Current Assets [Member] | Derivative Financial Instruments, Assets [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 6,940 14,001 18,460
Other Current Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Other Current Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 6,940 14,001 18,460
Other Current Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Other Noncurrent Assets [Member] | Money Market Funds [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 4,621 1,792 1,528
Other Noncurrent Assets [Member] | Money Market Funds [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 4,621 1,792 1,528
Other Noncurrent Assets [Member] | Money Market Funds [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Other Noncurrent Assets [Member] | Money Market Funds [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Other Noncurrent Assets [Member] | Mutual Fund [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 11,974 12,172 11,362
Other Noncurrent Assets [Member] | Mutual Fund [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 11,974 12,172 11,362
Other Noncurrent Assets [Member] | Mutual Fund [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Other Noncurrent Assets [Member] | Mutual Fund [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Other Noncurrent Assets [Member] | Derivative Financial Instruments, Assets [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 3,454 4,159 4,830
Other Noncurrent Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 1 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 0 0 0
Other Noncurrent Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 2 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value 3,454 4,159 4,830
Other Noncurrent Assets [Member] | Derivative Financial Instruments, Assets [Member] | Level 3 [Member]      
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]      
Total assets measured at fair value $ 0 $ 0 $ 0