Summary of Significant Accounting Policies - Other Assets and Other Liabilities (Narrative) (Details) - USD ($) $ in Millions	24 Months Ended
	Dec. 31, 2015	Dec. 31, 2024	Dec. 31, 2023
Significant Accounting Policies [Line Items]
Risk-sharing arrangement term	10 years
SPE, assets		$ 29	$ 28
SPE, liabilities		$ 3	$ 6
Minimum
Significant Accounting Policies [Line Items]
Percentage of losses assumed on pool of loans sold	1.00%
Maximum
Significant Accounting Policies [Line Items]
Percentage of losses assumed on pool of loans sold	2.25%