Income Taxes (Reconciliation of Changes to the Valuation Allowance) (Details) $ in Millions	12 Months Ended
Dec. 31, 2017 USD ($)
Income Taxes [Abstract]
Valuation allowance as of December 31, 2016	$ 1,476
Changes based on 2017 activity	(364)
Tax reform - rate change	(370)
Tax reform - AMT repeal	(68)
Release of prior uncertain tax position	(5)
Equity - windfall tax benefit release	59
Equity - pension benefits in OCI	4
Valuation allowance as of December 31, 2017	$ 732

Valuation Allowance, Deferred Tax Asset, Activity During Period

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- Definition

Valuation Allowance, Deferred Tax Asset, Alternative Minimum Tax Repeal

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- Definition

Valuation Allowance, Deferred Tax Asset, Change in Enacted Rate

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- Definition

Valuation Allowance, Deferred Tax Asset, Effect on Retained Earnings

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No definition available.

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- Definition

Valuation Allowance, Deferred Tax Asset, Pension Benefits in Other Comprehensive Income

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- Definition

Valuation Allowance, Deferred Tax Asset, Release of Uncertain Tax Position

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No definition available.

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- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84230637&loc=d3e32537-109319

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- References

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