Shareholders' Equity - Summary of Amount of Common Stock Repurchased by the Firm (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Equity [Abstract]
Common share repurchases	8.2	6.3
Average cost per share	$ 236.35	$ 197.08
Total cost of common share repurchases	$ 1,928	$ 1,250

Equity impact of the cost of common and preferred stock that were repurchased during the period. Recorded using the cost method.

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