Reconciliation of Tax Contingencies (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009		Dec. 31, 2008
Income Tax Contingency [Line Items]
Tax contingencies	$ 229	[1]	$ 213	[1]	$ 181	[1]	$ 166
Amount of tax contingencies, if fully recognized, which would decrease effective tax rate	$ 229

[1] As of December 31, 2011, we had $229 million of tax contingencies all of which, if fully recognized, would decrease our effective tax rate.