| **Fair Value Measurements - Fair Value of Life Policy Loans, Deferred Annuities, and Structured Settlements (Detail) - USD ($) $ in Millions** | Jun. 30, 2019 | Dec. 31, 2018 |
|------------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Fair value of life policy loans                                                                                                                | $ 42          | $ 40          |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 983           | 927           |
| Quoted prices in active markets for identical assets (Level 1)                                                                                 |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Fair value of life policy loans                                                                                                                | 0             | 0             |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 0             | 0             |
| Significant other observable inputs (Level 2)                                                                                                  |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Fair value of life policy loans                                                                                                                | 0             | 0             |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 205           | 185           |
| Significant unobservable inputs (Level 3)                                                                                                      |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Fair value of life policy loans                                                                                                                | 42            | 40            |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 778           | 742           |
| Deferred annuities                                                                                                                             |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 778           | 742           |
| Deferred annuities | Quoted prices in active markets for identical assets (Level 1)                                                            |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 0             | 0             |
| Deferred annuities | Significant other observable inputs (Level 2)                                                                             |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 0             | 0             |
| Deferred annuities | Significant unobservable inputs (Level 3)                                                                                 |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 778           | 742           |
| Structured settlements                                                                                                                         |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 205           | 185           |
| Structured settlements | Quoted prices in active markets for identical assets (Level 1)                                                        |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 0             | 0             |
| Structured settlements | Significant other observable inputs (Level 2)                                                                         |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | 205           | 185           |
| Structured settlements | Significant unobservable inputs (Level 3)                                                                             |          |          |
| **Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]**                                               |          |          |
| Liabilities Related to Investment Contracts, Fair Value Disclosure                                                                             | $ 0           | $ 0           |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.
+ References
No definition available.
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| - Definition
Fair value portion of liability related to investment contracts for example, but not limited to, guaranteed investment contract or annuities.
+ References
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| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Fair value portion of loan receivable, including, but not limited to, mortgage loans held for investment, finance receivables held for investment, policy loans on insurance contracts.
+ References
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