Unrecognized Tax Benefit (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Reconciliation of Unrecognized Tax Benefits [Line Items]
Gross unrecognized tax benefits at beginning of year	$ 0	$ 0	$ 2
Gross increase in prior year positions	0	0	0
Gross decrease in prior year positions	0	0	(2)
Gross increase in current year positions	0	0	0
Gross decrease in current year positions	0	0	0
Settlements with tax authorities	0	0	0
Decrease for lapse in applicable statute of limitations	0	0	0
Gross unrecognized tax benefits at end of year	$ 0	$ 0	$ 0

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

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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 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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The gross amount of decreases in unrecognized tax benefits resulting from lapses of the applicable statutes of limitations.

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