Loans - Summary of Changes in Allowance for Credit Losses (Detail) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|---|
Sep. 30, 2021 |
Sep. 30, 2020 |
Sep. 30, 2021 |
Sep. 30, 2020 |
Dec. 31, 2020 |
|
| Allowance for loan losses | |||||
| Balance, beginning of period | $ 3,271 | $ 3,901 | $ 3,874 | $ 2,168 | $ 2,168 |
| Net (charge-offs)/recoveries | (76) | (340) | (202) | (731) | |
| Provision | 164 | 153 | (281) | 2,502 | |
| Other | (27) | (59) | (225) | ||
| Balance, end of period | $ 3,332 | $ 3,714 | $ 3,332 | $ 3,714 | $ 3,874 |
| Allowance ratio | 2.60% | 3.70% | 2.60% | 3.70% | 3.70% |
| Net charge-off ratio | 0.20% | 1.30% | 0.20% | 1.00% | 0.90% |
| Allowance for losses on lending commitments | |||||
| Balance, beginning of period | $ 822 | $ 490 | $ 557 | $ 313 | $ 313 |
| Provision | 11 | 125 | 294 | 302 | |
| Other | (18) | ||||
| Balance, end of period | 833 | 615 | 833 | 615 | 557 |
| Wholesale [Member] | |||||
| Allowance for loan losses | |||||
| Balance, beginning of period | 2,173 | 2,757 | 2,584 | 1,331 | 1,331 |
| Net (charge-offs)/recoveries | (40) | (277) | (49) | (501) | |
| Provision | 25 | 102 | (345) | 1,977 | |
| Other | (27) | (59) | (225) | ||
| Balance, end of period | $ 2,131 | $ 2,582 | $ 2,131 | $ 2,582 | $ 2,584 |
| Allowance ratio | 1.80% | 2.80% | 1.80% | 2.80% | 2.70% |
| Net charge-off ratio | 0.10% | 1.20% | 0.10% | 0.70% | 0.60% |
| Allowance for losses on lending commitments | |||||
| Balance, beginning of period | $ 636 | $ 490 | $ 557 | $ 313 | $ 313 |
| Provision | 13 | 125 | 110 | 302 | |
| Other | (18) | ||||
| Balance, end of period | 649 | 615 | 649 | 615 | 557 |
| Consumer [Member] | |||||
| Allowance for loan losses | |||||
| Balance, beginning of period | 1,098 | 1,144 | 1,290 | 837 | 837 |
| Net (charge-offs)/recoveries | (36) | (63) | (153) | (230) | |
| Provision | 139 | 51 | 64 | 525 | |
| Balance, end of period | $ 1,201 | $ 1,132 | $ 1,201 | $ 1,132 | $ 1,290 |
| Allowance ratio | 12.40% | 16.10% | 12.40% | 16.10% | 15.90% |
| Net charge-off ratio | 1.60% | 3.70% | 2.40% | 4.50% | 4.20% |
| Allowance for losses on lending commitments | |||||
| Balance, beginning of period | $ 186 | ||||
| Provision | (2) | $ 184 | |||
| Balance, end of period | $ 184 | $ 184 | |||