Debt (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Debt Instrument [Line Items]
Senior unsecured notes, carrying value	$ 12,699.2
Senior unsecured notes, principal amount repurchased	21.2
Senior unsecured notes, repurchase price	24.2
Loss on extinguishment of debt	3.0	0
Unsecured surplus note, carrying amount	24.9
Senior Revolving Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	2,000.0
Line of credit maturity date	Sep. 29, 2016
Commercial Paper Program
Debt Instrument [Line Items]
Commercial paper authorized	2,500.0
Commercial paper	$ 758.6

Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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- Definition

Face (par) amount of the original debt instrument that was repurchased.

+ References

No definition available.

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- Definition

The cash outflow for the extinguishment of long-term borrowing, with the highest claim on the assets of the entity in case of bankruptcy or liquidation, before its maturity.

+ References

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

-Publisher FASB

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-Glossary Financing Activities

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

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Date the credit facility terminates, in CCYY-MM-DD format.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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- Definition

Financial instruments issued by insurance entities (surplus notes) that are includable in surplus for statutory accounting purposes as prescribed or permitted by state laws and regulations that are liabilities of the issuer.

+ References

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- Definition

Commercial Paper, Maximum Borrowing Capacity

+ References

No definition available.

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