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 ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2017
Jun. 30, 2016
Jun. 30, 2017
Jun. 30, 2016
Noncontrolling Interest [Line Items]        
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net       $ (4,806)
Common Stock, Dividends, Per Share, Cash Paid $ 0.18 $ 0.17 $ 0.36 $ 0.34
Balance, beginning of period     $ 1,581,511 $ 1,415,813
Net income (loss) $ (11,316) $ (7,873) 27,569 26,321
Other comprehensive income (loss):        
Unrealized holding gains (losses) on available-for-sale securities (4) 4 0 2
Derivative holding losses (6,157) (920) (7,762) (9,424)
Foreign currency translation adjustments 7,182 315 18,684 18,836
Cash dividends     (25,046) (23,689)
Issuance of common stock under employee stock plans, net     7,067 9,102
Stock-based compensation expense     5,719 5,453
Stock Repurchased During Period, Value (2,542)   (35,542)  
Balance, end of period $ 1,572,200 $ 1,437,608 $ 1,572,200 1,437,608
Parent [Member]        
Noncontrolling Interest [Line Items]        
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net       $ (4,806)
Common Stock, Dividends, Per Share, Cash Paid $ 0.18 $ 0.17 $ 0.36 $ 0.34
Balance, beginning of period     $ 1,560,820 $ 1,399,800
Net income (loss)     24,471 23,598
Other comprehensive income (loss):        
Unrealized holding gains (losses) on available-for-sale securities       2
Derivative holding losses     (7,567) (9,424)
Foreign currency translation adjustments     16,888 19,485
Cash dividends     (25,046) (23,689)
Issuance of common stock under employee stock plans, net     7,067 9,102
Stock-based compensation expense     5,719 5,453
Stock Repurchased During Period, Value     (35,542)  
Balance, end of period $ 1,546,810 $ 1,419,521 1,546,810 1,419,521
Non-controlling Interest [Member]        
Noncontrolling Interest [Line Items]        
Adjustment to Additional Paid in Capital, Income Tax Effect from Share-based Compensation, Net       0
Balance, beginning of period     20,691 16,013
Net income (loss)     3,098 2,723
Other comprehensive income (loss):        
Unrealized holding gains (losses) on available-for-sale securities       0
Derivative holding losses     (195) 0
Foreign currency translation adjustments     1,796 (649)
Cash dividends     0 0
Issuance of common stock under employee stock plans, net     0 0
Stock-based compensation expense     0 0
Stock Repurchased During Period, Value     0  
Balance, end of period $ 25,390 $ 18,087 $ 25,390 $ 18,087