Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Risk-sharing arrangement term		10 years
Special Purpose Entities, assets	$ 49,000,000	$ 63,000,000
Special Purpose Entities, liabilities	$ 22,000,000	25,000,000
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	$ 600,000	800,000	$ 600,000
Asset-backed securities issued, net
Significant Accounting Policies [Line Items]
Deferred debt issuance costs	0	542,000
Asset-backed securities issued, net | Accounting Standards Update 2015-03
Significant Accounting Policies [Line Items]
Deferred debt issuance costs	0	542,000
Long-term Debt
Significant Accounting Policies [Line Items]
Deferred debt issuance costs	7,081,000	10,438,000
Long-term Debt | Accounting Standards Update 2015-03
Significant Accounting Policies [Line Items]
Deferred debt issuance costs	$ (7,000,000)	$ 10,000,000
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