Share Repurchase Programs and Dividends - Share Repurchase Programs (Detail) $ / shares in Units, shares in Millions	3 Months Ended	9 Months Ended	39 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares shares	Sep. 30, 2017 USD ($) $ / shares shares
Equity [Abstract]
Number of share repurchase programs authorized			6
Stock repurchase programs, authorized amount	$ 11,000,000,000	$ 11,000,000,000	$ 11,000,000,000
Stock repurchase programs, remaining authorized amount	$ 677,000,000	$ 677,000,000	$ 677,000,000
Stock repurchased (in shares) | shares	7.7	29.4	257.7
Aggregate stock repurchase price	$ 362,000,000	$ 1,300,000,000	$ 10,300,000,000
Average cost per share (in dollars per share) | $ / shares	$ 46.97	$ 45.05	$ 40.05