Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Common stock, shares authorized	4,500,000,000
Common stock, par value	$ 0.01
Common stock, shares outstanding	1,275,312,404	1,307,330,369
Preferred stock, shares authorized	200,000,000
Preferred stock, par value	$ 0.01
Preferred stock, issued	0
Other comprehensive income (loss)	$ (1,652)	$ 1,334	$ (331)