Derivative Financial Instruments - Carrying Amount and Cumulative Basis Adjustments for Hedge Accounting (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Prepayable financial asset closed portfolio, amortized cost	$ 2,830	$ 3,300
Prepayable financial asset closed portfolio, last-of-layer, amortized cost	1,430	1,730
Cumulative adjustment associated with hedging relationships	11	21
Hedged Items Currently Designated | Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Hedged Assets/Liabilities	15,557	15,553
Cumulative Hedge Accounting Basis Adjustments	(139)	(76)
Hedged Items Currently Designated | Available-for-sale securities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Carrying Amount of Hedged Assets/Liabilities	23,637	22,804
Cumulative Hedge Accounting Basis Adjustments	(38)	99
De-designated | Long-term debt
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cumulative Hedge Accounting Basis Adjustments	68	72
De-designated | Available-for-sale securities
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Cumulative Hedge Accounting Basis Adjustments	$ 0	$ 0