Shareholders' Equity - Summary of Amount of Common Stock Repurchased by the Firm (Detail) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017 USD ($) $ / shares shares
Equity [Abstract]
Common share repurchases | shares	6.2
Average cost per share | $ / shares	$ 243.22
Total cost of common share repurchases | $	$ 1,500