Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended			24 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Risk-sharing arrangement term				10 years
SPE, assets	$ 28	$ 30
SPE, liabilities	$ 6	6
Employee Stock Purchase Plan, percentage of common stock fair value that employees can purchase			85.00%
Employees maximum 401(k) contribution	100.00%
Employer matching contributions	$ 2	$ 2	$ 1
Minimum
Significant Accounting Policies [Line Items]
Business purpose loans term	3 years
Business purpose maturity loan term	12 years
Percentage of losses assumed on pool of loans sold				1.00%
Incentive Plan, awards vesting period (in years)	3 years
Maximum
Significant Accounting Policies [Line Items]
Business purpose loans term	30 years
Business purpose maturity loan term	36 months
Percentage of losses assumed on pool of loans sold				2.25%
Incentive Plan, awards vesting period (in years)	4 years