- 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, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss beginning balance	$ (6,938)		$ (8,652)
Other comprehensive income before reclassifications	(792)		330
Amounts reclassified from accumulated other comprehensive loss	355		947
Total other comprehensive income (loss), net of tax	(437)	(76)	1,277	142
Accumulated other comprehensive loss ending balance	(7,375)		(7,375)
Investment income, net	595	375	1,008	1,182
Net income	4,190	15,333	4,410	14,628
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss beginning balance	(6,047)		(8,652)
Other comprehensive income before reclassifications	87		2,100
Amounts reclassified from accumulated other comprehensive loss	262		854
Total other comprehensive income (loss), net of tax	349		2,954
Accumulated other comprehensive loss ending balance	(5,698)		(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	50		248
Settlement cost	212		606
Net income	262		854
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	(891)		0
Other comprehensive income before reclassifications	(879)		(1,770)
Amounts reclassified from accumulated other comprehensive loss	93		93
Total other comprehensive income (loss), net of tax	(786)		(1,677)
Accumulated other comprehensive loss ending balance	(1,677)		(1,677)
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	93		93
Net income	$ 355		$ 947