Shareholders' Equity - AOCI (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' Equity Attributable to Parent, Beginning Balance	$ 457,015
Shareholders' Equity Attributable to Parent, Ending Balance	390,472	$ 457,015
Disproportionate tax effect	14,600
Deferred taxes provided for basis difference in foreign subsidiaries	0
Accumulated Other Comprehensive Loss, Net
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' Equity Attributable to Parent, Beginning Balance	(107,135)	(88,126)	$ (83,007)
Other comprehensive income (loss) before reclassification	53,504	(47,579)	(39,350)
Amounts reclassified from accumulated other comprehensive loss, net	20,036	28,570	34,231
Net current period other comprehensive (loss) income	73,540	(19,009)	(5,119)
Shareholders' Equity Attributable to Parent, Ending Balance	(33,595)	(107,135)	(88,126)
Foreign currency translation adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' Equity Attributable to Parent, Beginning Balance	(80,885)	(45,886)	(34,709)
Other comprehensive income (loss) before reclassification	56,511	(34,999)	(11,177)
Net current period other comprehensive (loss) income	56,511	(34,999)	(11,177)
Shareholders' Equity Attributable to Parent, Ending Balance	(24,374)	(80,885)	(45,886)
Deferred income tax expense (benefit)	(5,339)	(4,113)	(1,565)
Deferred tax expense (benefit) before reclassification	(1,226)	(2,548)	(1,565)
Unrealized (losses) gains on interest rate swap and foreign currency forward contracts
Accumulated Other Comprehensive Income (Loss) [Line Items]
Shareholders' Equity Attributable to Parent, Beginning Balance	(26,250)	(42,240)	(48,298)
Other comprehensive income (loss) before reclassification	(3,007)	(12,580)	(28,173)
Amounts reclassified from accumulated other comprehensive loss, net	20,036	28,570	34,231
Net current period other comprehensive (loss) income	17,029	15,990	6,058
Shareholders' Equity Attributable to Parent, Ending Balance	(9,221)	(26,250)	(42,240)
Deferred income tax expense (benefit)	16,317	9,269	(2,959)	$ (6,701)
Deferred tax expense (benefit) before reclassification	(1,245)	(9,619)	(17,402)
Deferred tax expense (benefit), reclassification from AOCI	$ 8,295	$ 21,847	$ 21,143