Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) at beginning of period	$ (13,296)	$ (10,773)	$ (22,617)	$ (20,836)
Other comprehensive income (loss) before reclassifications	402	3,174	10,315	14,736
Amounts reclassified from other comprehensive income	(1,035)	665	(1,627)	(834)
Net other comprehensive income (loss) during the period	(633)	3,839	8,688	13,902
Accumulated other comprehensive income (loss) at end of period	(13,929)	(6,934)	(13,929)	(6,934)
Unrealized Gains (Losses) on Available-For-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) at beginning of period	(4)	0	(4)	(2)
Other comprehensive income (loss) before reclassifications	0	(4)	0	(2)
Amounts reclassified from other comprehensive income	0	0	0	0
Net other comprehensive income (loss) during the period	0	(4)	0	(2)
Accumulated other comprehensive income (loss) at end of period	(4)	(4)	(4)	(4)
Unrealized Holding Gains (Losses) on Derivative Transactions [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) at beginning of period	(794)	(3,337)	6,773	6,087
Other comprehensive income (loss) before reclassifications	(7,391)	(319)	(14,366)	(8,244)
Amounts reclassified from other comprehensive income	(1,035)	665	(1,627)	(834)
Net other comprehensive income (loss) during the period	(8,426)	346	(15,993)	(9,078)
Accumulated other comprehensive income (loss) at end of period	(9,220)	(2,991)	(9,220)	(2,991)
Foreign Currency Translation Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated other comprehensive income (loss) at beginning of period	(12,498)	(7,436)	(29,386)	(26,921)
Other comprehensive income (loss) before reclassifications	7,793	3,497	24,681	22,982
Amounts reclassified from other comprehensive income	0	0	0	0
Net other comprehensive income (loss) during the period	7,793	3,497	24,681	22,982
Accumulated other comprehensive income (loss) at end of period	$ (4,705)	$ (3,939)	$ (4,705)	$ (3,939)