Stockholders' Equity (Comprehensive Income) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	$ 1,503,738	$ 1,815,314
Net current-period other comprehensive (loss) income, net of tax	(4,237)	9,597
Ending Balance	1,486,806	1,818,982
Change in Unrealized Gain (Loss) on Derivatives
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(944)	(919)
Other comprehensive income before reclassifications, before tax	1,309	214
Tax expense (benefit)	(314)	(51)
Other comprehensive income before reclassifications, net of tax	995	163
Reclassification of loss (gain) from accumulated other comprehensive income (loss), before tax	(1,319)	(1,471)
Reclassification of tax expense (benefit)	316	353
Reclassification of loss (gain) from accumulated other comprehensive income (loss), after tax	(1,003)	(1,118)
Net current-period other comprehensive (loss) income, net of tax	(8)	(955)
Ending Balance	(952)	(1,874)
Foreign Currency Translation Adjustments Gain (Loss)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(23,532)	46,232
Other comprehensive income before reclassifications, before tax	(4,229)	10,552
Tax expense (benefit)	0	0
Other comprehensive income before reclassifications, net of tax	(4,229)	10,552
Reclassification of loss (gain) from accumulated other comprehensive income (loss), before tax	0	0
Reclassification of tax expense (benefit)	0	0
Reclassification of loss (gain) from accumulated other comprehensive income (loss), after tax	0	0
Net current-period other comprehensive (loss) income, net of tax	(4,229)	10,552
Ending Balance	(27,761)	56,784
Accumulated Other Comprehensive (Loss) Income
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning Balance	(24,476)	45,313
Other comprehensive income before reclassifications, before tax	(2,920)	10,766
Tax expense (benefit)	(314)	(51)
Other comprehensive income before reclassifications, net of tax	(3,234)	10,715
Reclassification of loss (gain) from accumulated other comprehensive income (loss), before tax	(1,319)	(1,471)
Reclassification of tax expense (benefit)	316	353
Reclassification of loss (gain) from accumulated other comprehensive income (loss), after tax	(1,003)	(1,118)
Net current-period other comprehensive (loss) income, net of tax	(4,237)	9,597
Ending Balance	$ (28,713)	$ 54,910