Quarterly report pursuant to Section 13 or 15(d)

Non-Controlling Interest Non-Controlling Interest (Schedule of Equity) (Details)

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Non-Controlling Interest Non-Controlling Interest (Schedule of Equity) (Details) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Noncontrolling Interest [Line Items]        
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification     $ 14,100,000  
Common Stock, Dividends, Per Share, Cash Paid $ 0.22 $ 0.18 $ 0.44 $ 0.36
Balance, beginning of period     $ 1,652,259,000 $ 1,581,511,000
Net income $ 10,495,000 $ (11,316,000) 59,224,000 27,569,000
Other comprehensive income (loss):        
Unrealized holding gains on available-for-sale securities 0 (4,000) 4,000 0
Derivative holding losses 20,553,000 (6,157,000) 15,646,000 (7,762,000)
Foreign currency translation adjustments (18,262,000) 7,182,000 (12,003,000) 18,684,000
Cash dividends     (30,856,000) (25,046,000)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders     (21,332,000)  
Issuance of common stock under employee stock plans, net     10,840,000 7,067,000
Stock-based compensation expense     6,599,000 5,719,000
Stock Repurchased During Period, Value (22,007,000) (2,542,000) (40,106,000) (35,542,000)
Balance, end of period $ 1,654,375,000 $ 1,572,200,000 1,654,375,000 1,572,200,000
Parent [Member]        
Noncontrolling Interest [Line Items]        
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification     14,100,000  
Common Stock, Dividends, Per Share, Cash Paid $ 0.44 $ 0.36    
Balance, beginning of period     1,621,951,000 1,560,820,000
Net income     54,844,000 24,471,000
Other comprehensive income (loss):        
Unrealized holding gains on available-for-sale securities     4,000  
Derivative holding losses     15,120,000 (7,567,000)
Foreign currency translation adjustments     (12,096,000) 16,888,000
Cash dividends     (30,856,000) (25,046,000)
Issuance of common stock under employee stock plans, net     10,840,000 7,067,000
Stock-based compensation expense     6,599,000 5,719,000
Stock Repurchased During Period, Value     (40,106,000) (35,542,000)
Balance, end of period $ 1,640,400,000 $ 1,546,810,000 1,640,400,000 1,546,810,000
Non-controlling Interest [Member]        
Noncontrolling Interest [Line Items]        
New Accounting Pronouncement or Change in Accounting Principle, Effect of Adoption, Quantification     0  
Balance, beginning of period     30,308,000 20,691,000
Net income     4,380,000 3,098,000
Other comprehensive income (loss):        
Unrealized holding gains on available-for-sale securities     0  
Derivative holding losses     526,000 (195,000)
Foreign currency translation adjustments     93,000 1,796,000
Cash dividends       0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders     (21,332,000)  
Issuance of common stock under employee stock plans, net     0 0
Stock-based compensation expense     0 0
Stock Repurchased During Period, Value     0 0
Balance, end of period $ 13,975,000 $ 25,390,000 $ 13,975,000 $ 25,390,000