Accumulated Other Comprehensive Income (Loss) - Schedules of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ 370,638	$ 335,338
Ending Balance	442,937	370,638
Scenario, Previously Reported
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance		(34,176)
Unrealized Gains on Investments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	421	346
Other comprehensive income (loss) before reclassifications	257	135
Amounts reclassified from AOCI, net of tax	(62)	(60)
Net other comprehensive income (loss)	195	75
Ending Balance	616	421
Cumulative Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(29,084)	(23,257)
Other comprehensive income (loss) before reclassifications	17,058	(5,827)
Amounts reclassified from AOCI, net of tax	0	0
Net other comprehensive income (loss)	17,058	(5,827)
Ending Balance	(12,026)	(29,084)
Unrecognized Net Actuarial Loss and Prior Service Credit, Net
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(10,728)	(11,265)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from AOCI, net of tax	(430)	537
Net other comprehensive income (loss)	(430)	537
Ending Balance	(11,158)	(10,728)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(39,391)	(34,176)
Other comprehensive income (loss) before reclassifications	17,315	(5,692)
Amounts reclassified from AOCI, net of tax	(492)	477
Net other comprehensive income (loss)	16,823	(5,215)
Ending Balance	$ (22,568)	$ (39,391)