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Investments (Narrative) (Detail) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2019 USD ($) Security partnerships | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($)
Investment [Line Items] |  |  |  |
Document Period End Date |  | Dec. 31, 2019 |  |
Net unrealized appreciation (depreciation) included in OCI |  | $ 3 | $ (4) |
AOCI Portion Attributable to change of FV of investments with OTTI |  | (18) | $ 1 |
Portion of gross unrealized loss represented by the United States Treasury and Agency obligations |  | $ 61 |  |
Moodys historical mean recovery rate |  | 42.00% |  |
Limited partnerships number | partnerships |  | 131 |  |
Number of fixed maturities in an unrealized loss position | Security |  | 4,091 |  |
Total number of fixed maturities | Security |  | 31,203 |  |
Largest single unrealized loss in the fixed maturities |  | $ 6 |  |
Restricted assets in fixed maturities and short-term investments |  | $ 21,000 |  |
Percentage of mortgage-backed securities represented by investments in US government agency bonds |  | 83.00% | 81.00% |
Restricted assets in cash |  | $ 109 | $ 93 |
Huatai Group [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Ownership Percentage |  | 30.90% | 20.00% |
Corporate securities |  |  |  |
Investment [Line Items] |  |  |  |
Credit losses recognized in net income |  | $ 37 | $ 25 | $ 5
Company assumed recovery rate |  | 32.00% |  |
Collateralized Mortgage Backed Securities [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Credit losses recognized in net income |  | $ 0 | $ 0 |
CHINA | Huatai Group [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Ownership Percentage |  | 31.00% | 20.00% |
CHINA | Huatai Life Insurance Co. [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Ownership Percentage |  | 20.00% | 20.00% |
Subsequent Event [Member] | CHINA | Huatai Group [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Equity method investment, additional 15.3 ownership percentage obtained | 15.30% |  |  |
Equity method investment, additional 7.1 percentage obtained | 7.10% |  |  |
Indirect Ownership [Member] | CHINA | Huatai Group [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Ownership Percentage |  | 30.90% |  |
Indirect Ownership [Member] | CHINA | Huatai Life Insurance Co. [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Ownership Percentage |  | 25.00% |  |
Direct Ownership [Member] | CHINA | Huatai Life Insurance Co. [Member] |  |  |  |
Investment [Line Items] |  |  |  |
Ownership Percentage |  | 20.00% |  |

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