Fair Value of Assets and Liabilities - Charged-Off Receivable transfers (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2018	Jun. 30, 2017
Transfer of Financial Assets Accounted for as Sales [Line Items]
Aggregate Unpaid Balance	$ 37,593	$ 76,178
Proceeds	5,038	10,171
Amount recovered on transferred Charged-Off Receivables	3,461	6,680
Bank Partner loans
Transfer of Financial Assets Accounted for as Sales [Line Items]
Aggregate Unpaid Balance	37,469	74,895
Proceeds	5,021	10,000
Loan receivables held for sale
Transfer of Financial Assets Accounted for as Sales [Line Items]
Aggregate Unpaid Balance	124	1,283
Proceeds	$ 17	$ 171	$ 0