Equity - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended
	Apr. 30, 2017	Mar. 31, 2017	Mar. 31, 2016
Stock repurchase program, remaining authorized repurchase amount		$ 2,140
Number of shares repurchased		9,000,000	2,000,000
Cash paid for shares repurchased		$ 420	$ 75
Scenario, Forecast
Number of shares repurchased	1,184,682
Cash paid for shares repurchased	$ 60