Stockholders' Equity - Additional Information (Detail) - USD ($)		1 Months Ended		3 Months Ended		12 Months Ended
	Apr. 24, 2017	Mar. 31, 2017	Feb. 28, 2017	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 11, 2015	Oct. 23, 2014	Jul. 25, 2013
Stockholders Equity [Line Items]
Dividends declared per common share				$ 0.31	$ 0.28
Cost of treasury stock		$ 2,000,000,000		$ 2,000,000,000			$ 500,000,000	$ 1,000,000,000	$ 500,000,000
Cumulative shares repurchased		34,767,377		34,767,377		33,837,526
Average price of common stock purchased		$ 45.15	$ 45.30	$ 46.14		$ 46.16
Payments For Repurchase Of Common Stock		$ 1,604,000,000		$ 1,604,000,000
Maximum
Stockholders Equity [Line Items]
Cost of treasury stock		$ 2,000,000,000		$ 2,000,000,000
Subsequent Event
Stockholders Equity [Line Items]
Declaration Date	Apr. 24, 2017
Dividends declared per common share	$ 0.34
Cash dividend, date to be Paid	Jun. 16, 2017
Cash dividend, recorded date	Jun. 02, 2017