Accumulated Other Comprehensive (Loss) Income - Summary of components of accumulated other comprehensive (loss) income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive (Loss) Income
Pension adjustment, Balance at the beginning	$ (12,981)	$ (9,933)
Pension adjustment, Change during period
Pension adjustment, Before-tax amount	(2,688)	(4,800)
Pension adjustment, Tax (expense) benefit	981	1,752
Pension adjustment, net of taxes	(1,707)	(3,048)	(1,350)
Pension adjustment, Balance at the ending	(14,688)	(12,981)	(9,933)
Unrealized gain (loss) on securities, Balance at beginning	187	501
Unrealized gain (loss) on securities, change during period
Unrealized gain (loss) on securities, Before-tax amount	(249)	(495)
Unrealized gain (loss) on securities, Tax (expense) benefit	91	181
Unrealized gain (loss) on securities, Total activity	(158)	(314)
Unrealized gain (loss) on securities, balance at ending	29	187	501
Foreign currency translation, Balance at beginning	148	286
Foreign currency translation, Change during period
Foreign currency translation, Before-tax amount	180	(218)
Foreign currency translation, Tax (expense) benefit	85	80
Foreign currency translation	265	(138)	209
Foreign currency translation, Balance at ending	413	148	286
Net loss on cash flow hedge, Balance at beginning		(387)
Net loss on cash flow hedge, Change during period
Net loss on cash flow hedge, Before-tax amount		610
Net loss on cash flow hedge, Tax (expense) benefit		(223)
Net loss on cash flow hedge, Total activity		387	133
Net loss on cash flow hedge, Balance at ending			(387)
Total, Balance at opening	(12,646)	(9,533)
Total, Change during period
Total, Before-tax amount	(2,757)	(4,903)
Total, Tax (expense) benefit	1,157	1,790	146,015
Total activity	(1,600)	(3,113)
Total, Balance at ending	$ (14,246)	$ (12,646)	$ (9,533)