Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 2,604	$ 11,860	$ 11,076	$ (370)	$ 12,499	$ 9,643	$ 11,872	$ 8,015	$ 25,170	$ 42,029	$ 26,481
Net income									25,170
Other comprehensive (loss) income, net of tax:
Changes in pension liability and other post-retirement benefit obligations									(83,887)	68,328	(43,702)
Tax effect of changes in pension liability and other post-retirement benefit obligations									31,924	(25,653)	14,455
Change in market value of securities									0	7,113	(14,948)
Tax effect of change in market value of securities									0	(3,041)	6,054
Foreign currency translation adjustments									(1,928)	(2,510)	362
Other comprehensive (loss) income									(53,891)	44,237	(37,779)
Comprehensive (loss) income	$ (50,188)	$ 10,880	$ 11,186	$ (599)	$ 54,450	$ 7,694	$ 12,691	$ 11,431	$ (28,721)	$ 86,266	$ (11,298)