- 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, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss beginning balance	$ (8,555)		$ (8,652)
Other comprehensive income before reclassifications	1,122		1,122
Total other comprehensive income (loss), net of tax	1,617	(220)	1,714	218
Accumulated other comprehensive loss ending balance	(6,938)		(6,938)
Defined Benefit Pension Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss beginning balance	(8,555)		(8,652)
Other comprehensive income before reclassifications	2,013		2,013
Total other comprehensive income (loss), net of tax	2,508		2,605
Accumulated other comprehensive loss ending balance	(6,047)		(6,047)
Defined Benefit Pension Items | Amortization of loss included in net periodic cost
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss	101		198
Defined Benefit Pension Items | Settlement cost included in net periodic cost
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss	394		394
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	0		0
Other comprehensive income before reclassifications	(891)		(891)
Total other comprehensive income (loss), net of tax	(891)		(891)
Accumulated other comprehensive loss ending balance	(891)		(891)
Unrealized Gains and Losses on Available-for-Sale Securities | Amortization of loss included in net periodic cost
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss	0		0
Unrealized Gains and Losses on Available-for-Sale Securities | Settlement cost included in net periodic cost
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Amounts reclassified from accumulated other comprehensive loss	$ 0		$ 0