Accumulated Other Comprehensive Income (Loss) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period			$ (270,850)
Other comprehensive income (loss) before reclassifications			1,249
Amounts reclassified from accumulated other comprehensive income (loss)			11,492
Total other comprehensive income, net of tax	19,219	7,620	12,741	10,986
Balance at the end of the period	(258,109)		(258,109)
Pension and other postretirement plans
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period			(266,042)
Amounts reclassified from accumulated other comprehensive income (loss)			13,976
Total other comprehensive income, net of tax			13,976
Balance at the end of the period	(252,066)		(252,066)
Unrealized gain/(loss) on hedges
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period			(4,203)
Other comprehensive income (loss) before reclassifications			3,532
Amounts reclassified from accumulated other comprehensive income (loss)			(1,631)
Total other comprehensive income, net of tax			1,901
Balance at the end of the period	(2,302)		(2,302)
Foreign currency translation adjustment
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period			(1,502)
Other comprehensive income (loss) before reclassifications			(2,239)
Total other comprehensive income, net of tax			(2,239)
Balance at the end of the period	(3,741)		(3,741)
Unrealized gain on investments
Changes in accumulated other comprehensive income (loss) by component
Balance at the beginning of the period			897
Other comprehensive income (loss) before reclassifications			(44)
Amounts reclassified from accumulated other comprehensive income (loss)			(853)
Total other comprehensive income, net of tax			$ (897)