Other Comprehensive Loss - Related Tax Effects Allocated to Each Component of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Equity [Abstract]
Retirement benefits adjustment, before tax amount	$ (957)	$ 143
Cumulative translation adjustment, before tax amount	1,822	305
Total other comprehensive income (loss), before tax amount	865	448
Retirement benefits adjustment, tax	217	(34)
Cumulative translation adjustment, tax	0	0
Total other comprehensive income (loss), tax	217	(34)
Retirement benefits adjustment, after tax amount	(740)	109
Cumulative translation adjustment, after tax amount	1,822	305
Total other comprehensive income (loss)	$ 1,082	$ 414