Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended	12 Months Ended
	Oct. 15, 2019	May 31, 2014	Dec. 31, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2014	Dec. 31, 2013
Significant Accounting Policies [Line Items]
Risk-sharing arrangement term							10 years
SPE, assets			$ 48,000	$ 48,000	$ 47,000
SPE, liabilities			14,000	$ 14,000	17,000
Incentive Plan, awards vesting period (in years)	2 years
Incentive Plan, mandatory holding period before awards vest		3 years
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				$ 700	600	$ 500
Lease liability			13,443	13,443	0
Right-of-use asset			$ 11,866	$ 11,866	$ 0
Minimum
Significant Accounting Policies [Line Items]
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]
Percentage of losses assumed on pool of loans sold							2.25%
Incentive Plan, awards vesting period (in years)		4 years
5 Arches, LLC
Significant Accounting Policies [Line Items]
Minority interest, percentage					20.00%
Variable Interest Entity, Primary Beneficiary
Significant Accounting Policies [Line Items]
VIE, ownership interest rate			80.00%