Share-Based Payments - Data Related to All Stock Option Activity (Detail) - USD ($) $ / shares in Units, $ in Millions |
12 Months Ended | ||||
|---|---|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||
| Weighted-average grant-date fair value per stock option (in dollars per share) | $ 5.06 | $ 4.01 | $ 3.89 | ||
| Aggregate intrinsic value on exercise | $ 625 | $ 331 | $ 389 | ||
| Cash received upon exercise | [1] | 1,259 | 862 | 1,019 | |
| Tax benefits realized related to exercise | 115 | 95 | 112 | ||
| Employee Stock Option [Member] | |||||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||
| Total compensation cost related to nonvested stock options not yet recognized, pre-tax | $ 5 | $ 10 | $ 58 | ||
| Weighted-average period over which stock option compensation cost is expected to be recognized (years) | 1 year 8 months | 9 months 18 days | 1 year 1 month 6 days | ||
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