Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net income (loss)	$ 220	$ 13,632	$ 4,087	$ 5,509	$ (95,709)	$ 9,540	$ 6,431	$ (2,086)	$ 23,448	$ (81,824)	$ (5,633)
Other comprehensive (loss) income:
Foreign currency translation adjustment									(6,228)	(4,364)	(2,108)
Reclassification of loss on cash flow hedges, net of tax									143	(143)	0
Adjustment to retirement benefit liability, net of tax									49	(24)	53
Adjustment to post-retirement healthcare benefit liability, net of tax									171	(1,435)	45
Other comprehensive loss									(5,865)	(5,966)	(2,010)
Total comprehensive income (loss)									$ 17,583	$ (87,790)	$ (7,643)