Equity - Share Repurchases (Detail) - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Equity [Abstract] | ||
| Number of shares repurchased | 19 | 9 |
| Cash paid for shares repurchased | $ 1,327 | $ 420 |
| Average cost per share | $ 68.74 | $ 50.15 |