Reconciliation of Unrecognized Tax Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reconciliation of Unrecognized Tax Benefits [Line Items]
Unrecognized tax benefits at January 1	$ 262.6	$ 252.6	$ 230.0
Increases for positions taken in current year	14.8	13.5	14.8
Increases for positions taken in a prior year	21.0	2.3	14.9
Decreases for positions taken in a prior year	(0.7)	(1.0)	(4.3)
Decreases for settlements with taxing authorities	(0.8)	(1.4)	(1.7)
Decreases for lapses in the applicable statute of limitations	(11.3)	(3.4)	(1.1)
Unrecognized tax benefits at December 31	$ 285.6	$ 262.6	$ 252.6

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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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-Name Accounting Standards Codification

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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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