Accumulated Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ (150,776)	$ (134,648)	$ (152,193)	$ (140,363)
Other comprehensive (loss) income before reclassifications	(5,808)	(3,529)	(10,300)	(3,214)
Amounts reclassified from accumulated other comprehensive income (net of tax)	2,955	2,701	8,864	8,101
Net current-period other comprehensive (loss) income	(2,853)	(828)	(1,436)	4,887
Ending balance	(153,629)	(135,476)	(153,629)	(135,476)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI, Pension and Other Postretirement Benefit Plans, Tax	(1,881)	(1,719)	(5,644)	(5,158)
Foreign Currency
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(4,208)	6,968	284	6,653
Other comprehensive (loss) income before reclassifications	(5,808)	(3,529)	(10,300)	(3,214)
Amounts reclassified from accumulated other comprehensive income (net of tax)	0	0	0	0
Net current-period other comprehensive (loss) income	(5,808)	(3,529)	(10,300)	(3,214)
Ending balance	(10,016)	3,439	(10,016)	3,439
Pension and Other Postretirement Benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(146,568)	(141,616)	(152,477)	(147,016)
Other comprehensive (loss) income before reclassifications	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (net of tax)	2,955	2,701	8,864	8,101
Net current-period other comprehensive (loss) income	2,955	2,701	8,864	8,101
Ending balance	$ (143,613)	$ (138,915)	$ (143,613)	$ (138,915)