Credit Concentrations - Credit Concentration, Government and Federal Agency Obligations (Detail) - USD ($) $ in Millions |
9 Months Ended | 12 Months Ended |
|---|---|---|
Sep. 30, 2021 |
Dec. 31, 2020 |
|
| U.S. Government and Agency Obligations Held By The Firm [Member] | ||
| Concentration Risk [Line Items] | ||
| Concentration risk, Credit risk, Financial instrument, Maximum exposure | $ 147,262 | $ 187,009 |
| Concentration risk, Credit risk, Financial instrument, Maximum exposure, As a percentage of total Assets | 10.20% | 16.10% |
| Non-U.S. Government and Agency Obligations Held By The Firm [Member] | ||
| Concentration Risk [Line Items] | ||
| Concentration risk, Credit risk, Financial instrument, Maximum exposure | $ 58,520 | $ 59,580 |
| Concentration risk, Credit risk, Financial instrument, Maximum exposure, As a percentage of total Assets | 4.10% | 5.10% |