Fair Value Disclosures - Additional Information (Detail) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
|
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] | ||
| Collateralized loan obligations outstanding borrowings maturity year | 2030 | |
| Fair Value Option [Member] | ||
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] | ||
| Total investments | $ 35 | $ 37 |
| Significant Unobservable Inputs (Level 3) [Member] | Private/ Public Equity [Member] | Consolidated Variable Interest Entities [Member] | ||
| Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] | ||
| Total investments | $ 252 | $ 194 |