Reconciliation of Beginning and Ending Amount of Unrecognized Tax Benefits (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Income Tax Contingency [Line Items]
Balance, beginning of year	$ 24	[1]	$ 17	[1]
Additions for tax positions of prior years	7		7
Settlements	0		0
Reductions for tax positions of prior years	0		0
Balance, end of year	$ 31	[1]	$ 24	[1]

[1] Amounts do not include tax deductions of $10 at December 31, 2011, $8 at December 31, 2010, and $6 at January 1, 2010.