Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	3 Months Ended				12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Statement of Comprehensive Income [Abstract]
Net income	$ 23,632	$ 38,104	$ 21,712	$ 25,250	$ 44,450	$ 108,698	$ 162,071
Other comprehensive income (loss)
Foreign currency translation adjustment					(229)	145	(14,942)
Deferred gain on available for sale securities					729	265	27
Current period cash flow hedging activity, net of $477 tax expense in 2013, $2,471 tax expense in 2012 and $266 tax expense in 2011					810	7,658	2,395
Reclassification of hedging activities into earnings, net of $95 tax benefit in 2013, $2,630 tax expense in 2012 and $2,668 tax benefit in 2011					152	(2,757)	9,155
Current period pension and postretirement plan adjustment, net of $5,531 tax expense in 2013, $1,553 tax benefit in 2012, and $7,391 tax benefit in 2011					8,022	(1,716)	(18,977)
Current period curtailment gain into earnings, net of $718 tax expense in 2013					(983)	0	0
Reclassification of pension and postretirement adjustments into earnings, net of $740 tax benefit in 2013, $2,056 tax benefit in 2012 and $1,900 tax benefit in 2011					1,101	5,885	6,704
Comprehensive income					$ 54,052	$ 118,178	$ 146,433