Significant Accounting Policies Common Stock Repurchase Program (Details) (USD $) In Millions, unless otherwise specified	6 Months Ended
Jun. 30, 2013
Accelerated Share Repurchases, Settlement (Payment) or Receipt	$ 250
Stock Repurchased During Period, Shares	1.9
Stock Repurchased During Period, Value	110.0
cumulative common stock repurchased through repurchase program	21.1
cumulative value of shares repurchased through stock repurchase program	690
Stock Repurchase Program, Remaining Authorized Repurchase Amount	120
May 2013 Accelerated Share repurchase [Domain]
Accelerated Share Repurchases, Settlement (Payment) or Receipt	$ 100

cumulative common stock repurchased through repurchase program

No definition available.

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- Definition

cumulative value of shares repurchased through stock repurchase program

+ References

No definition available.

+ Details

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- Definition

Amount of cash payment to or cash receipt from the bank; or the stock issuance to or stock received from the bank in the settlement of the accelerated share repurchase agreement.

+ References

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

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 99-7

-Paragraph 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21463-112644

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Research Bulletin (ARB)

-Number 43

-Section B

-Paragraph 11A

-Chapter 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 29, 30

-Article 5

+ Details

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Balance Type:	na
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- Definition

Equity impact of the value of stock that has been repurchased during the period and has not been retired and is not held in treasury. Some state laws may mandate the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

+ References

+ Details

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Balance Type:	debit
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- Definition

The remaining repurchase amount authorized by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

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Balance Type:	credit
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