Comprehensive Income (Accumulated Other Comprehensive Loss, Net of Tax) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	$ (260,530)	$ (483,576)	$ (386,963)
Other comprehensive income before reclassifications	(155,675)	171,681	(113,453)
Amounts reclassified from accumulated other comprehensive loss	11,877	23,984	16,840
Recognition of net actuarial loss for pension settlement costs		27,381
Net current-period other comprehensive income (loss)	(143,798)	223,046	(96,613)
Balance, ending	(404,328)	(260,530)	(483,576)
Pension Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	(411,432)	(697,874)	(575,163)
Other comprehensive income before reclassifications	(140,832)	205,341	(152,402)
Amounts reclassified from accumulated other comprehensive loss	19,996	36,938	29,691
Recognition of net actuarial loss for pension settlement costs		44,163
Net current-period other comprehensive income (loss)	(120,836)	286,442	(122,711)
Balance, ending	(532,268)	(411,432)	(697,874)
Postretirement Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	(5,230)	(74,264)	(41,811)
Other comprehensive income before reclassifications	(112,525)	67,289	(29,922)
Amounts reclassified from accumulated other comprehensive loss	(995)	1,745	(2,531)
Net current-period other comprehensive income (loss)	(113,520)	69,034	(32,453)
Balance, ending	(118,750)	(5,230)	(74,264)
Deferred Taxes On Pension And OPEB Costs [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	156,280	288,712	230,161
Other comprehensive income before reclassifications	97,534	(100,951)	68,871
Amounts reclassified from accumulated other comprehensive loss	(7,124)	(14,699)	(10,320)
Recognition of net actuarial loss for pension settlement costs		(16,782)
Net current-period other comprehensive income (loss)	90,410	(132,432)	58,551
Balance, ending	246,690	156,280	288,712
All Other [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance, beginning	(148)	(150)		(150)
Other comprehensive income before reclassifications	148	2
Net current-period other comprehensive income (loss)	148	2
Balance, ending		$ (148)		$ (150)

Other comprehensive income, Recognition of net actuarial loss for pension settlement costs, before tax

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Amount before tax of increase (decrease) in accumulated in equity from transactions and other events and circumstances from non-owner sources. Excludes net income (loss), and accumulated changes in equity from transactions resulting from investments by owners (distributions to owners).

+ References

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Amount before tax and reclassification adjustments of other comprehensive income (loss).

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Amount before tax, after reclassification adjustments of other comprehensive income (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 1A

-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669619-108580

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 220

-SubTopic 10

-Section 45

-Paragraph 1B

-URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669625-108580

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 45

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=35755396&loc=d3e33775-111570

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Amount before tax of reclassification adjustments of other comprehensive income (loss).

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