Derivatives and Hedging Activities - Carrying Amount of Hedged Items Currently Designated in a Hedging Relationship and Related Cumulative Hedging Adjustment (Detail) - Accounted for as hedges - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Investments
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Value	$ 85,149	$ 42,449
Cumulative Hedging Adjustment, Assets	(236)	244
Deposits
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Value	503	762
Cumulative Hedging Adjustment, Liabilities	(17)	(17)
Unsecured short-term borrowings
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Value	7,345	4,694
Cumulative Hedging Adjustment, Liabilities	(84)	(25)
Unsecured long-term borrowings
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Value	163,404	143,082
Cumulative Hedging Adjustment, Liabilities	$ (8,023)	$ (7,340)

Derivatives and Hedging Activities - Carrying Amount of Hedged Items Currently Designated in a Hedging Relationship and Related Cumulative Hedging Adjustment (Detail) - Accounted for as hedges - USD ($)
$ in Millions

Mar. 31, 2026

Dec. 31, 2025

Derivative Instruments and Hedging Activities Disclosures [Line Items]

Carrying Value

$ 85,149

$ 42,449

Cumulative Hedging Adjustment, Assets

(236)

244

Deposits

Derivative Instruments and Hedging Activities Disclosures [Line Items]

Carrying Value