Summary of Changes in Accumulated Other Comprehensive Loss for Pension Plan Items (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning balance	$ (7,777)	$ (8,555)	$ (7,517)	$ (8,652)
Other comprehensive income (loss) before reclassifications	196	1,122	(540)	1,122
Amounts reclassified from accumulated other comprehensive loss	466	495	942	592
Total other comprehensive income, net of tax	662	1,617	402	1,714
Accumulated other comprehensive loss, beginning balance	(7,115)	(6,938)	(7,115)	(6,938)
Income before equity in loss from unconsolidated affiliates and income taxes	23,310	2,713	533,212	248
Investment income, net	3,951	306	4,224	413
Income tax benefit	(8,690)	0	(115,594)	0
Net income	14,609	2,698	417,597	221
Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Net income	466	495	942	592
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning balance	(5,415)	(8,555)	(5,392)	(8,652)
Other comprehensive income (loss) before reclassifications	(115)	2,013	(367)	2,013
Amounts reclassified from accumulated other comprehensive loss	200	495	429	592
Total other comprehensive income, net of tax	85	2,508	62	2,605
Accumulated other comprehensive loss, beginning balance	(5,330)	(6,047)	(5,330)	(6,047)
Defined Benefit Pension Items | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amortization of loss	125	101	257	198
Settlement cost	200	394	440	394
Income before equity in loss from unconsolidated affiliates and income taxes	325	495	697	592
Income tax benefit	(125)	0	(268)	0
Net income	200	495	429	592
Unrealized Gains and Losses on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss, beginning balance	(2,362)	0	(2,125)	0
Other comprehensive income (loss) before reclassifications	311	(891)	(173)	(891)
Amounts reclassified from accumulated other comprehensive loss	266	0	513	0
Total other comprehensive income, net of tax	577	(891)	340	(891)
Accumulated other comprehensive loss, beginning balance	(1,785)	(891)	(1,785)	(891)
Unrealized Gains and Losses on Available-for-Sale Securities | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Investment income, net	432	0	833	0
Income tax benefit	(166)	0	(320)	0
Net income	$ 266	$ 0	$ 513	$ 0