Shareholders' Equity - Additional Information (Detail) - USD ($)		3 Months Ended
	Apr. 18, 2019	Mar. 31, 2019	Mar. 31, 2018	Dec. 11, 2015	Oct. 23, 2014	Jul. 25, 2013
Stockholders Equity [Line Items]
Dividends declared per common share		$ 0.35	$ 0.34
Cost of treasury stock		$ 2,000,000,000		$ 500,000,000	$ 1,000,000,000	$ 500,000,000
Cumulative shares repurchased		39,426,521
Average price of common stock purchased		$ 44.95
Payments for repurchase of common stock		$ 1,772,000,000
Repurchases of common stock		0
Maximum
Stockholders Equity [Line Items]
Cost of treasury stock		$ 2,000,000,000
Subsequent Event
Stockholders Equity [Line Items]
Declaration Date	Apr. 18, 2019
Dividends declared per common share	$ 0.35
Cash dividend, date to be Paid	Jun. 19, 2019
Cash dividend, recorded date	Jun. 05, 2019