Comprehensive Income (Reclassification Out of AOCI) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Dec. 31, 2013	Jun. 30, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes	$ 56,714		$ (57,215)		$ 113,177			$ 26,843
Tax impact	(19,034)		18,755		(36,223)			(14,520)
Net income	37,680		(38,460)		76,954		103,155	12,323
Reclassification out of Accumulated Other Comprehensive Income [Member] | Pension Benefits [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior-service costs	(11)	[1],[2]	(2)	[1],[2]	(22)	[1],[2]		(4)	[1],[2]
Actuarial gains/(losses)	(4,819)	[1],[2]	(10,072)	[1],[2]	(9,638)	[1],[2]		(20,144)	[1],[2]
Income before income taxes	(4,830)	[1],[2]	(10,074)	[1],[2]	(9,660)	[1],[2]		(20,148)	[1],[2]
Tax impact	1,835	[1],[2]	3,828	[1],[2]	3,671	[1],[2]		7,656	[1],[2]
Net income	(2,995)	[1],[2]	(6,246)	[1],[2]	(5,989)	[1],[2]		(12,492)	[1],[2]
Reclassification out of Accumulated Other Comprehensive Income [Member] | Postretirement Costs [Member] | Amortization Of Defined Benefit Cost Items [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Prior-service costs	890	[1],[2]	1,525	[1],[2]	1,780	[1],[2]		3,050	[1],[2]
Actuarial gains/(losses)	(722)	[1],[2]	(2,228)	[1],[2]	(1,444)	[1],[2]		(4,456)	[1],[2]
Income before income taxes	168	[1],[2]	(703)	[1],[2]	336	[1],[2]		(1,406)	[1],[2]
Tax impact	(64)	[1],[2]	267	[1],[2]	(128)	[1],[2]		534	[1],[2]
Net income	$ 104	[1],[2]	$ (436)	[1],[2]	$ 208	[1],[2]		$ (872)	[1],[2]

[1] Amounts in parentheses indicate losses.

[2] These accumulated other comprehensive loss components are included in the computation of net periodic pension and OPEB costs (see Note 14 - Retirement Plans for additional details).