Earnings Per Share - Additional Information (Detail) - USD ($) shares in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Feb. 28, 2018	Nov. 30, 2016	Jul. 31, 2012
Earnings Per Share [Abstract]
Anti-dilutive securities excluded from computation of EPS	2.0	3.0
Stock repurchase program, authorized amount					$ 2,000,000,000
Stock repurchase program, additional authorized amount			$ 1,500,000,000	$ 1,500,000,000
Share repurchases	7.7
Value of share repurchases	$ 522,000,000
Remaining value available under stock repurchase programs	$ 2,100,000,000