Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Comprehensive Income
Net income	$ 6,667	$ 6,793	$ (83,353)
Other comprehensive income:
Adjustment to pension liability	1,672	1,501
Tax expense	(669)	(600)
Adjustment to pension liability, net of tax	1,003	901
Foreign currency translation adjustments	(1,130)	886
Total other comprehensive income (loss), net of tax	(127)	1,787
Comprehensive income	6,540	8,580
Defined Benefit Pension Items
Balance at the beginning of the period	(54,431)	(48,705)	(48,705)
Other comprehensive loss (income), net of tax, before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income, net of tax	1,003	901
Net current period other comprehensive income (loss), net of tax	1,003	901
Balance at the end of the period	(53,428)	(47,804)	(54,431)
Foreign Currency Items
Balance at the beginning of the period	4,697	3,382	3,382
Other comprehensive loss (income), net of tax, before reclassifications	(1,130)	886
Amounts reclassified from accumulated other comprehensive income, net of tax	0	0
Net current period other comprehensive income (loss), net of tax	(1,130)	886
Balance at the end of the period	3,567	4,268	4,697
Total
Balance at the beginning of the period	(49,734)	(45,323)	(45,323)
Other comprehensive loss (income), net of tax, before reclassifications	(1,130)	886
Amounts reclassified from accumulated other comprehensive income, net of tax	1,003	901
Net current period other comprehensive income (loss), net of tax	(127)	1,787
Balance at the end of the period	$ (49,861)	$ (43,536)	$ (49,734)