Share Repurchase Programs and Dividends - Share Repurchase Programs (Detail) $ / shares in Units, shares in Millions	3 Months Ended	45 Months Ended
	Mar. 31, 2018 USD ($) $ / shares shares	Mar. 31, 2018 USD ($) program $ / shares shares
Equity [Abstract]
Number of share repurchase programs authorized | program		6
Stock repurchase programs, authorized amount	$ 11,000,000,000	$ 11,000,000,000
Stock repurchase programs, remaining authorized amount	$ 0	$ 0
Stock repurchased (in shares) | shares	8.4	270.7
Aggregate stock repurchase price	$ 450,000,000	$ 11,000,000,000
Average cost per share (in dollars per share) | $ / shares	$ 53.32	$ 40.63