Stockholder's Equity (Details 2) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017	Mar. 31, 2017	Dec. 31, 2016
Summary of accumulated other comprehensive income/(loss) [Line Items]
Unrecognized gains (losses) on foreign currency translation	$ (90,369)	$ (110,581)	$ (170,596)	$ (173,496)
Unrecognized losses on equity investments	0	0	(5,449)	5,120
Unrecognized actuarial losses	(884)	(884)	(1,153)	(1,153)
Unrecognized losses on cash flow hedges	0	0	(2)	(2)
Totals	(91,253)	$ (111,465)	(177,200)	$ (169,531)
Other comprehensive income before reclassification adjustments
Summary of accumulated other comprehensive income/(loss) [Line Items]
Unrecognized gains (losses) on foreign currency translation	20,212		2,900
Unrecognized losses on equity investments	0		(10,569)
Unrecognized actuarial losses	0		0
Unrecognized losses on cash flow hedges	0		0
Totals	20,212		(7,669)
Net current period other comprehensive income
Summary of accumulated other comprehensive income/(loss) [Line Items]
Unrecognized gains (losses) on foreign currency translation	20,212		2,900
Unrecognized losses on equity investments	0		(10,569)
Unrecognized actuarial losses	0		0
Unrecognized losses on cash flow hedges	0		0
Totals	$ 20,212		$ (7,669)