Indebtedness (Summary Of Total Indebtedness) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
2007 Facility
Commercial paper
Total debt	1,236.8	1,243.8
Current portion	(99.4)	(71.3)
Total long-term debt	1,137.4	1,172.5
Fair value of interest rate swap	8.4	12.6
Series 2005-1 Notes [Member]
Debt Instrument [Line Items]
Notes Payable	308.2	311.5
Fair value of interest rate swap	8.2	11.5
Series 2007-1 Notes [Member]
Debt Instrument [Line Items]
Notes Payable	300.0	300.0
2010 Senior Notes [Member]
Debt Instrument [Line Items]
Notes Payable	497.3	497.3
Unamortized discount	2.7	2.7
2008 Term Loan [Member]
Debt Instrument [Line Items]
Loan Payable	$ 131.3	$ 135.0

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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Sum of the carrying values as of the balance sheet date of all debt, including all short-term borrowings, long-term debt, and capital lease obligations.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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Fair value of derivative asset, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

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