Fair Value Measurements - Fair Value of Life Policy Loans, Deferred Annuities, and Structured Settlements (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of life policy loans	$ 51	$ 44
Liabilities Related to Investment Contracts, Fair Value Disclosure	1,028	982
Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
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
Fair value of life policy loans	0	0
Liabilities Related to Investment Contracts, Fair Value Disclosure	223	212
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Fair value of life policy loans	51	44
Liabilities Related to Investment Contracts, Fair Value Disclosure	805	770
Deferred annuities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities Related to Investment Contracts, Fair Value Disclosure	805	770
Deferred annuities | Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
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
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
Liabilities Related to Investment Contracts, Fair Value Disclosure	805	770
Structured settlements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities Related to Investment Contracts, Fair Value Disclosure	223	212
Structured settlements | Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
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
Liabilities Related to Investment Contracts, Fair Value Disclosure	223	212
Structured settlements | Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis
Liabilities Related to Investment Contracts, Fair Value Disclosure	$ 0	$ 0