Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Condensed Consolidated Statements of Comprehensive Income (unaudited) [Abstract]
Net income	$ 17,678	$ 14,917
Other comprehensive income:
Change in unrecognized pension and post-retirement benefit costs	0	28
Income tax benefit on change in unrecognized pension and post-retirement benefit costs	0	27
Foreign currency translation adjustments	1,730	(6,258)
Income tax (provision) benefit on foreign currency translation adjustments	(335)	350
Other comprehensive income (loss)	1,395	(5,853)
Comprehensive income	19,073	9,064
Comprehensive income (loss) attributable to non-controlling interest	60	(537)
Comprehensive income attributable to controlling interest	$ 19,013	$ 9,601