Arrangements with Navient Corporation Arrangements with Navient Corporation (Details) - USD ($)		3 Months Ended	12 Months Ended
	Apr. 30, 2014	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Remaining balance of indemnification receivable in connection with the spin-off	$ 27,000,000		$ 24,000,000
Minimum days past due for spin off loan purchase			90 days
Period of hardship forbearance			6 months
Gains on sales of loans, net			$ 2,060,000	$ 0	$ 230,000
Interest income from third party				300,000	300,000
Gain (loss) resulting from loans sold				0	0
Write-down to fair value for loans sold to third party				5,000,000	6,000,000
Participated loans
Related Party Transaction [Line Items]
Loans sold to third party				$ 12,000,000	$ 16,000,000
Minimum
Related Party Transaction [Line Items]
Agreements with Navient, period of term (or less)	1 year
Maximum
Related Party Transaction [Line Items]
Agreements with Navient, period of term (or less)	2 years
Discontinued Operations, Disposed of by Sale
Related Party Transaction [Line Items]
Principal Amount Outstanding of Loans Held-in-portfolio		$ 43,000,000
Gains on sales of loans, net		$ 2,000,000