Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions |
Sep. 30, 2026 |
Dec. 31, 2025 |
Sep. 30, 2025 |
|---|---|---|---|
| Significant Accounting Policies [Line Items] | |||
| Fair value of loaned securities held | $ 11,600 | $ 13,300 | |
| Fair value of collateral loan under these securities lending agreements | 12,500 | 14,400 | |
| Separate account collateral held under securities lending agreements | 5,465 | $ 7,922 | |
| Fair value of securities received as collateral have been resold or repledged | $ 0 | $ 0 | |
| Minimum [Member] | |||
| Significant Accounting Policies [Line Items] | |||
| Collateral cash and securities received in exchange of value of securities lent in order to reduce counterparty risk | 102.00% | ||
| Maximum [Member] | |||
| Significant Accounting Policies [Line Items] | |||
| Collateral cash and securities received in exchange of value of securities lent in order to reduce counterparty risk | 112.00% |