Income Taxes (Details 4) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Tabular reconciliation of the total amounts of unrecognized tax benefits
Balance at January 1	$ 168.0	$ 150.4	$ 129.5
Increases related to prior periods	11.4	23.1	32.9
Decreases related to prior periods	(49.0)	(6.1)	(26.7)
Increases related to current period	34.4	23.7	17.4
Decreases related to settlements with taxing authorities	(4.8)	(14.1)	(1.1)
Decreases related to lapse of statute of limitations	(1.6)	(9.0)	(1.6)
Balance at December 31	$ 158.4	$ 168.0	$ 150.4

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The gross amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns as of the balance sheet date.

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