Derivative Financial Instruments - Impact on Derivatives and Hedged Items on Consolidated Statement of Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of gain (loss) on derivative recognized in consolidated statement of income	$ (30)	$ 72	$ 12	$ 68
Amount of gain (loss) on hedged item recognized in consolidated statement of income	30	(72)	(11)	(68)
Net unrealized gains (losses) on available-for-sale securities designated in fair value hedges, net of related taxes	(43)	115	32	34
Interest Rate Contract One
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of gain (loss) on derivative recognized in consolidated statement of income	(59)	156	43	43
Amount of gain (loss) on hedged item recognized in consolidated statement of income	59	(156)	(42)	(43)
Interest Rate Contract Two
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of gain (loss) on derivative recognized in consolidated statement of income	24	(84)	(36)	25
Amount of gain (loss) on hedged item recognized in consolidated statement of income	(24)	84	36	(25)
Foreign exchange contracts
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Amount of gain (loss) on derivative recognized in consolidated statement of income	5	0	5	0
Amount of gain (loss) on hedged item recognized in consolidated statement of income	$ (5)	$ 0	$ (5)