Accumulated Other Comprehensive Income Accumulated Other Comprehensive Income (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), Beginning Balance	$ 245		$ (245)
Other comprehensive income before reclassifications	(246)		476
Amounts reclassified from accumulated other comprehensive income	(1)		14
Accumulated other comprehensive income (loss), Ending Balance	(2)		245
Pension and Retiree Health and Welfare Benefit Items [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), Beginning Balance	251	[1]	(241)	[1]
Other comprehensive income before reclassifications	(250)	[1]	478	[1]
Amounts reclassified from accumulated other comprehensive income	(1)	[1]	14	[1]
Accumulated other comprehensive income (loss), Ending Balance	0	[1]	251	[1]
Equity Method Investments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive income (loss), Beginning Balance	(6)		(4)
Other comprehensive income before reclassifications	4		(2)
Amounts reclassified from accumulated other comprehensive income	0		0
Accumulated other comprehensive income (loss), Ending Balance	$ (2)		$ (6)

[1] Amounts are net of tax. See Note 13 for additional details.