Deferred Income Tax Assets and Liabilities (Parenthetical) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred tax assets, net operating losses	$ 47	[1]	$ 43	[1]
Deferred tax assets, net operating losses	289	[2]	113	[2]
Deferred tax assets, tax credits	12	[3]	7	[3]
Net operating losses-stock-based compensation
Schedule of Deferred Income Tax Assets and Liabilities [Line Items]
Deferred tax assets, net operating losses	9		116
Deferred tax assets, net operating losses	2		13
Deferred tax assets, tax credits	$ 146		$ 278

[1] Excluding $9 million and $116 million of deferred tax assets at December 31, 2012 and 2011, related to net operating losses that result from excess stock-based compensation and for which any benefit realized will be recorded to stockholders' equity.

[2] Excluding $2 million and $13 million of deferred tax assets at December 31, 2012 and 2011, related to net operating losses that result from excess stock-based compensation and for which any benefit realized will be recorded to stockholders' equity.

[3] Excluding $146 million and $278 million of deferred tax assets at December 31, 2012 and 2011, related to tax credits that result from excess stock-based compensation and for which any benefit realized will be recorded to stockholders' equity.