Equity - Share Repurchases (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		51 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016
Equity [Abstract]
Number of shares repurchased	2	4	200
Cash paid for shares repurchased	$ 75	$ 209	$ 7,310
Effective average cost per delivered share	$ 43.96	$ 47.51	$ 36.71