Common Shareholders' Equity (ESOP) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Stock Ownership Plan [Abstract]
Defined Contribution Plan, Cost Recognized	$ 59	$ 46	$ 44
ESOP-related unearned compensation at original issue price	14
ESOP-related unearned compensation at closing price as of end of period	$ 103

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The value of ESOP-related unearned compensation included as a reduction of common shareholders' equity, representing unallocated shares at the original issue price.

+ References

No definition available.

+ Details

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- Definition

The amount of the cost recognized during the period for defined contribution plans.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 70

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6414718&loc=d3e28014-114942

+ Details

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- Definition

The fair value of shares held by the ESOP as of the balance sheet date in which no ESOP participant has a vested interest and no lender has a claim. The fair value of an ESOP share is the amount the seller could reasonably expect to receive for it in a current sale between a willing buyer and a willing seller, that is, other than in a forced or liquidation sale, which would be the market price of the stock if it is publicly traded.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 50

-Paragraph 1

-Subparagraph (e)

-URI http://asc.fasb.org/extlink&oid=6418621&loc=d3e17540-113929

+ Details

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