Comprehensive Income, Reclassification Out of AOCI (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Dec. 31, 2012	Jun. 30, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	$ (57,215)		$ 33,716		$ 26,843			$ 82,900
Tax impact	(18,755)		11,717		14,520			30,411
Net income (loss)	(38,460)		21,999		12,323		100,825	52,489
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension Costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(10,074)	[1],[2]	(7,737)	[1],[2]	(20,148)	[1],[2]		(15,473)	[1],[2]
Tax impact	3,828	[1],[2]	2,940	[1],[2]	7,656	[1],[2]		5,880	[1],[2]
Net income (loss)	(6,246)	[1],[2]	(4,797)	[1],[2]	(12,492)	[1],[2]		(9,593)	[1],[2]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension Costs [Member] | Prior-service Costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(2)	[1],[2]	50	[1],[2]	(4)	[1],[2]		100	[1],[2]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension Costs [Member] | Actuarial Gains/(Losses) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(10,072)	[1],[2]	(7,787)	[1],[2]	(20,144)	[1],[2]		(15,573)	[1],[2]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Postretirement Costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	(703)	[1],[2]	592	[1],[2]	(1,406)	[1],[2]		1,184	[1],[2]
Tax impact	267	[1],[2]	(225)	[1],[2]	534	[1],[2]		(450)	[1],[2]
Net income (loss)	(436)	[1],[2]	367	[1],[2]	(872)	[1],[2]		734	[1],[2]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Postretirement Costs [Member] | Prior-service Costs [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	1,525	[1],[2]	2,503	[1],[2]	3,050	[1],[2]		5,006	[1],[2]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Postretirement Costs [Member] | Actuarial Gains/(Losses) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	$ (2,228)	[1],[2]	$ (1,911)	[1],[2]	$ (4,456)	[1],[2]		$ (3,822)	[1],[2]

[1] These accumulated other comprehensive loss components are included in the computation of net periodic pension cost (see Note 16 - Retirement Plans for additional details).

[2] Amounts in parentheses indicate losses.