Rollforward of Gross Consolidated Liability for Unrecognized Income Tax Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation of Provision of Income Taxes [Line Items]
Unrecognized tax benefits, beginning of year	$ 230.3	$ 197.1	$ 218.5
Tax positions related to current year:
Additions	42.0	47.6	52.1
Reductions	(1.8)	0	0
Tax positions related to prior years:
Additions	14.0	23.7	4.6
Reductions	(71.0)	(20.2)	(66.7)
Settlements	(3.3)	(5.0)	(2.9)
Lapses in statutes of limitations	(13.4)	(12.9)	(8.5)
Unrecognized tax benefits, end of year	$ 196.8	$ 230.3	$ 197.1

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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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The gross amount of decreases in unrecognized tax benefits resulting from tax positions that have been or will be taken in the tax return for the current period, excluding amounts pertaining to examined tax returns.

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The gross amount of decreases in unrecognized tax benefits resulting from tax positions taken in prior period tax returns, excluding amounts pertaining to examined tax returns.

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The gross amount of decreases in unrecognized tax benefits resulting from settlements with taxing authorities.

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The gross amount of increases in unrecognized tax benefits resulting from tax positions that have been or will be taken in the tax return for the current period, excluding amounts pertaining to examined tax returns.

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