Fair Value Measurements - Fair Values of Deferred Annuities, Structured Settlements and Other Items (Detail) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	$ 1,047	$ 1,045
Deferred annuities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	844	839
Structured Settlements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	203	206
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 insurance liabilities	0	0
Quoted prices in active markets for identical assets (Level 1) | Deferred annuities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	0	0
Quoted prices in active markets for identical assets (Level 1) | Structured Settlements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	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 insurance liabilities	203	206
Significant other observable inputs (Level 2) | Deferred annuities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	0	0
Significant other observable inputs (Level 2) | Structured Settlements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	203	206
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	844	839
Significant unobservable inputs (Level 3) | Deferred annuities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	844	839
Significant unobservable inputs (Level 3) | Structured Settlements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value of life insurance liabilities	$ 0	$ 0