Deferred Income Tax Assets and Liabilities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred tax assets, net operating losses	$ 156	[1]	$ 93	[1]
Deferred tax assets, tax credits	7	[2]	14	[2]
Net operating losses-stock-based compensation
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred tax assets, net operating losses	129		18
Deferred tax assets, tax credits	$ 278		$ 231

[1] Excluding $129 million and $18 million of deferred tax assets at December 31, 2011 and 2010, related to net operating losses that result from excess stock based compensation.

[2] Excluding $278 million and $231 million of deferred tax assets at December 31, 2011 and 2010, related to tax credits that result from excess stock based compensation.