Operating Expenses - Components of Operating Expenses (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Other Income and Expenses [Abstract]
Fixed compensation expense									$ 22,111	$ 24,332	$ 35,093
Variable compensation expense									20,574	16,581	12,606
Equity compensation expense									10,141	9,093	11,921
Total compensation expense									52,826	50,006	59,620
Systems and consulting									7,073	9,037	10,212
Loan acquisition costs									5,022	5,744	10,326
Office costs									4,248	4,550	5,270
Accounting and legal									2,842	3,658	4,837
Corporate costs									1,856	2,106	2,049
Other operating expenses									3,289	3,284	5,102
Operating expenses before restructuring charges									77,156	78,385	97,416
Restructuring charges								$ 10,000	0	10,401	0
Total Operating Expenses	$ 20,367	$ 19,922	$ 18,641	$ 18,226	$ 17,824	$ 20,355	$ 20,155	30,452	77,156	88,786	97,416
Upfront costs associated with hiring new executive officer									2,000
Restructuring Cost and Reserve [Line Items]
Restructuring charges								$ 10,000	$ 0	10,401	$ 0
Fixed Compensation Expense
Other Income and Expenses [Abstract]
Restructuring charges										5,000
Restructuring Cost and Reserve [Line Items]
Restructuring charges										5,000
Equity Compensation Expense
Other Income and Expenses [Abstract]
Restructuring charges										3,000
Restructuring Cost and Reserve [Line Items]
Restructuring charges										3,000
Contract Termination Costs
Other Income and Expenses [Abstract]
Restructuring charges										2,000
Restructuring Cost and Reserve [Line Items]
Restructuring charges										$ 2,000