Income Taxes (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010
Notes to Financial Statements [Abstract]
Effective tax rates (in hundredths)	19.60%	23.10%
Realized tax benefits associated with tax planning strategies	$ 18.4
Adjustments of certain historical tax benefits	12.2
Reduction in tax provision from finalization of prior year tax returns	4.8
Income tax benefits recorded for repayment of 2.5% convertible debentures	$ 75.0

A ratio calculated by dividing the reported amount of income tax expense attributable to continuing operations for the period by GAAP-basis pretax income from continuing operations.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 109

-Paragraph 47

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Subparagraph 2

-Article 4

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Namespace Prefix:	us-gaap
Data Type:	us-types:percentItemType
Balance Type:	na
Period Type:	duration