Fair Values of Assets and Liabilities - Assets Measured at Fair Value on Nonrecurring Basis (Details) - Fair Value, Measurements, Nonrecurring - USD ($) $ in Millions	Sep. 30, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	$ 625	$ 354
Other assets	16	27
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Other assets	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	0	0
Other assets	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Loans	625	354
Other assets	$ 16	$ 27