Basis of Presentation and Summary of Significant Accounting Policies Basis of Presentation and Sumnary of Significant Accounting Policies (Details 6) - USD ($) $ / shares in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
New Accounting Pronouncement, Early Adoption [Line Items]
Net income (loss)	$ 338,000,000	$ 205,000,000	$ 143,000,000	$ 192,000,000	$ 188,000,000	$ 188,000,000	$ 193,000,000	$ 203,000,000	$ 878,000,000	$ 772,000,000	$ (239,000,000)
Total current assets	(2,650,000,000)				(2,696,000,000)				(2,650,000,000)	(2,696,000,000)
Other, net	(660,000,000)				(679,000,000)				(660,000,000)	(679,000,000)
Long-term debt	(18,722,000,000)				(19,953,000,000)				(18,722,000,000)	(19,953,000,000)
Deferred income taxes, net	(3,569,000,000)				(3,154,000,000)				(3,569,000,000)	(3,154,000,000)
Pension Plan
New Accounting Pronouncement, Early Adoption [Line Items]
Fair value of plan assets valued at NAV	5,293,000,000				5,749,000,000				5,293,000,000	5,749,000,000
Fair value of plan assets	11,072,000,000				12,571,000,000				11,072,000,000	12,571,000,000	12,346,000,000	$ 12,321,000,000
Post-Retirement Benefit Plans
New Accounting Pronouncement, Early Adoption [Line Items]
Fair value of plan assets valued at NAV	153,000,000				264,000,000				153,000,000	264,000,000
Fair value of plan assets	$ 193,000,000				353,000,000				$ 193,000,000	353,000,000	535,000,000	$ 626,000,000
Restatement adjustment | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncement, Early Adoption [Line Items]
Net income (loss)										$ 0	$ 0
Earnings per share, basic and diluted										$ 0	$ 0
Total current assets					880,000,000					$ 880,000,000
Other, net					164,000,000					164,000,000
Long-term debt					168,000,000					168,000,000
Deferred income taxes, net					876,000,000					876,000,000
Net cash provided by operating activities										0	$ 0
Restatement adjustment | New Accounting Pronouncement, Early Adoption, Effect | Pension Plan
New Accounting Pronouncement, Early Adoption [Line Items]
Fair value of plan assets					0					0
Restatement adjustment | New Accounting Pronouncement, Early Adoption, Effect | Post-Retirement Benefit Plans
New Accounting Pronouncement, Early Adoption [Line Items]
Fair value of plan assets					$ 0					$ 0