Stockholders' Equity - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended	12 Months Ended			0 Months Ended
	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Feb. 09, 2015
Schedule Of Stockholders Equity [Line Items]
Value of shares authorized to repurchase program	$ 750	$ 1,100	$ 750
Shares repurchased		20.3	4.9
Weighted average price per share for common shares repurchased		$ 80.45	$ 64.98
Total cost of common shares repurchased		1,636	316	320
Remaining capacity for authorized repurchase shares		79
Dividends paid	256	735
Dividends paid per share	$ 1.35	$ 4.00
Dividends record date		Mar. 05, 2015	Dec. 13, 2013
Quarterly cash dividend per share		$ 1.400
Special dividend per share		$ 2.60
Accrued dividends related to unvested equity awards		12
Dividends declared date		Feb. 09, 2015
Dividends payable date		Mar. 26, 2015
Subsequent Event [Member]
Schedule Of Stockholders Equity [Line Items]
Value of shares authorized to repurchase program					$ 750
Quarterly cash dividend per share					$ 0.375