Accumulated Other Comprehensive Income (Loss), Net of Tax (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (37,955)	$ (25,290)	$ (8,895)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Other comprehensive gain (loss) before reclassifications	17,787	(13,049)	(16,559)
Amounts reclassified from accumulated other comprehensive loss	260	384	164
Net current-period other comprehensive gain (loss)	18,047	(12,665)	(16,395)
Ending Balance	(19,908)	(37,955)	(25,290)
Accumulated Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(37,119)	(24,988)	(10,088)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Other comprehensive gain (loss) before reclassifications	17,597	(12,131)	(14,900)
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Net current-period other comprehensive gain (loss)	17,597	(12,131)	(14,900)
Ending Balance	(19,522)	(37,119)	(24,988)
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(836)	(302)	1,193
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax [Abstract]
Other comprehensive gain (loss) before reclassifications	190	(918)	(1,659)
Amounts reclassified from accumulated other comprehensive loss	260	384	164
Net current-period other comprehensive gain (loss)	450	(534)	(1,495)
Ending Balance	$ (386)	$ (836)	$ (302)