Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Comprehensive Income
Net income (loss)	$ 8,309	$ (109,705)	$ 14,976	$ (102,912)	$ (83,353)
Other comprehensive income (loss):
Adjustment to pension liability	1,672	1,501	3,344	3,002
Tax expense	(669)	(600)	(1,338)	(1,200)
Adjustment to pension liability, net of tax	1,003	901	2,006	1,802
Foreign currency translation adjustments	(589)	(915)	(1,719)	(29)
Total other comprehensive income (loss), net of tax	414	(14)	287	1,773
Comprehensive income (loss)	8,723	(109,719)	15,263	(101,139)
Defined Benefit Pension Items
Balance at the beginning of the period			(54,431)	(48,705)	(48,705)
Other comprehensive loss, net of tax, before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive income, net of tax			2,006	1,802
Net current period other comprehensive income (loss), net of tax			2,006	1,802
Balance at the end of the period	(52,425)	(46,903)	(52,425)	(46,903)	(54,431)
Foreign Currency Items
Balance at the beginning of the period			4,697	3,382	3,382
Other comprehensive loss, net of tax, before reclassifications	(589)	(915)	(1,719)	(29)
Amounts reclassified from accumulated other comprehensive income, net of tax			0	0
Net current period other comprehensive income (loss), net of tax			(1,719)	(29)
Balance at the end of the period	2,978	3,353	2,978	3,353	4,697
Total
Balance at the beginning of the period			(49,734)	(45,323)	(45,323)
Other comprehensive loss, net of tax, before reclassifications			(1,719)	(29)
Amounts reclassified from accumulated other comprehensive income, net of tax			2,006	1,802
Net current period other comprehensive income (loss), net of tax			287	1,773
Balance at the end of the period	$ (49,447)	$ (43,550)	$ (49,447)	$ (43,550)	$ (49,734)