Fair Value Measurements - Quantitative Information about Nonrecurring Fair Value Measurement of Assets and Liabilities Classified as Level 3 (Detail) - Fair Value, Nonrecurring $ in Millions	Jun. 30, 2026 USD ($)	Dec. 31, 2025 USD ($)
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	$ 893	$ 1,713
Commercial Loans
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	342	342
Level 3
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	342	342
Level 3 \| Commercial Loans
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Total assets at fair value on a non-recurring basis	$ 342	$ 342
Loss severity rates \| Level 3 \| Commercial Loans \| Minimum \| Valuation of third-party appraisal on underlying collateral
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs	0.04	0
Loss severity rates \| Level 3 \| Commercial Loans \| Maximum \| Valuation of third-party appraisal on underlying collateral
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs	1	1
Loss severity rates \| Level 3 \| Commercial Loans \| Weighted Average \| Valuation of third-party appraisal on underlying collateral
Fair Value, Assets and Liabilities Measured on a Nonrecurring Basis [Line Items]
Range of Inputs	0.33	0.30