v3.19.3.a.u2
Share-Based Payments - Impact on Net Income (Detail) - 2019 Stock Plan [Member] - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based payment expense $ 718 $ 949 $ 840
Tax benefit for share-based compensation expense (137) (180) (163)
Share-based payment expense, net of tax 581 769 677
Total Shareholder Return Units (TSRUs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based payment expense 294 302 221
Restricted Stock Units (RSUs) [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based payment expense 275 286 301
Portfolio Performance Shares [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based payment expense 114 276 209
Performance Shares [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based payment expense 28 62 47
Share-based Payment Arrangement, Option [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based payment expense 7 12 55
Directors' compensation [Member]      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Share-based payment expense $ 0 $ 10 $ 7