Stockholder's Equity (Details 4) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Summary of accumulated other comprehensive income/(loss) [Line Items]
Unrecognized gains (losses) on foreign currency translation	$ (110,581)	$ (173,496)	$ (85,484)
Unrecognized gain/(loss) on equity investments	0	5,120	0
Unrecognized actuarial losses	(884)	(1,153)	(1,343)
Unrecognized gains (losses) on cash flow hedges	0	(2)	(1,416)
Totals	(111,465)	(169,531)	$ (88,243)
Other comprehensive income before reclassification adjustments
Summary of accumulated other comprehensive income/(loss) [Line Items]
Unrecognized gains (losses) on foreign currency translation	62,915	(90,528)
Unrecognized gain/(loss) on equity investments	0	5,120
Unrecognized actuarial losses	269	190
Unrecognized gains (losses) on cash flow hedges	2	1,414
Totals	63,186	(83,804)
Reclassification adjustment for write down of equity investment
Summary of accumulated other comprehensive income/(loss) [Line Items]
Unrecognized gains (losses) on foreign currency translation	0
Unrecognized gain/(loss) on equity investments	(5,120)
Unrecognized actuarial losses	0
Unrecognized gains (losses) on cash flow hedges	0
Totals	(5,120)
Reclassification amount to net income
Summary of accumulated other comprehensive income/(loss) [Line Items]
Unrecognized gains (losses) on foreign currency translation		2,516
Unrecognized gain/(loss) on equity investments		0
Unrecognized actuarial losses		0
Unrecognized gains (losses) on cash flow hedges		0
Totals		2,516
Net current period other comprehensive income
Summary of accumulated other comprehensive income/(loss) [Line Items]
Unrecognized gains (losses) on foreign currency translation	62,915	(88,012)
Unrecognized gain/(loss) on equity investments	(5,120)	5,120
Unrecognized actuarial losses	269	190
Unrecognized gains (losses) on cash flow hedges	2	1,414
Totals	$ 58,066	$ (81,288)