Summary of Changes in Accumulated Other Comprehensive Loss for Pension Plan Items (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning balance	$ (7,115)	$ (6,938)	$ (7,517)	$ (8,652)
Other comprehensive income (loss) before reclassifications	(1,911)	(606)	(2,451)	516
Amounts reclassified from accumulated other comprehensive loss	1,192	169	2,134	761
Total other comprehensive (loss) income, net of tax	(719)	(437)	(317)	1,277
Accumulated other comprehensive loss, beginning balance	(7,834)	(7,375)	(7,834)	(7,375)
Investment income, net	3,367	595	7,592	1,008
Realized loss (gain) on sale	0	93	(833)	93
(Loss) income before equity in loss from unconsolidated affiliates and income taxes	(531)	4,360	532,682	4,607
Income tax benefit	386	(158)	(115,209)	(158)
Net (loss) income	(156)	4,190	417,441	4,410
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net (loss) income	1,192	169	2,134	761
Defined benefit pension items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning balance	(5,330)	(6,047)	(5,392)	(8,652)
Other comprehensive income (loss) before reclassifications	58	87	(309)	2,100
Amounts reclassified from accumulated other comprehensive loss	396	262	825	854
Total other comprehensive (loss) income, net of tax	454	349	516	2,954
Accumulated other comprehensive loss, beginning balance	(4,876)	(5,698)	(4,876)	(5,698)
Defined benefit pension items | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amortization of loss	115	50	373	248
Settlement cost	529	212	969	606
(Loss) income before equity in loss from unconsolidated affiliates and income taxes	644	262	1,342	854
Income tax benefit	(248)	0	(517)	0
Net (loss) income	396	262	825	854
Items related to available-for-sale securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning balance	(1,785)	(891)	(2,125)	0
Other comprehensive income (loss) before reclassifications	(1,969)	(693)	(2,142)	(1,584)
Amounts reclassified from accumulated other comprehensive loss	796	(93)	1,309	(93)
Total other comprehensive (loss) income, net of tax	(1,173)	(786)	(833)	(1,677)
Accumulated other comprehensive loss, beginning balance	(2,958)	(1,677)	(2,958)	(1,677)
Items related to available-for-sale securities | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Realized loss (gain) on sale	0	(93)	833	(93)
Income tax benefit	(499)	0	(819)	0
Net (loss) income	796	(93)	1,309	(93)
Other-than-temporary impairment losses | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Investment income, net	1,295	0	1,295	0
(Loss) income before equity in loss from unconsolidated affiliates and income taxes	$ 1,295	$ (93)	$ 2,128	$ (93)