Arrangements with Navient Corporation (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Related Party Transaction [Line Items]
Minimum days past due that company may required spin-off company to purchase loans			90 days
Period of hardship forbearance			6 months
Split loans, net	$ 13,725,959,000		$ 13,725,959,000		$ 10,515,505,000
Interest income from related party	60,000	$ 200,000	300,000	$ 400,000
Gains on loans to related party	0	0	0	0
Write-down to fair value for loans sold to related party	1,400,000	1,900,000	5,000,000	5,600,000
Split Loans
Related Party Transaction [Line Items]
Split loans, net	71,000,000		71,000,000
Participated loans
Related Party Transaction [Line Items]
Loans sold to related party	$ 3,600,000	$ 6,600,000	$ 13,100,000	$ 21,100,000