Arrangements with Navient Corporation (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 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	$ 12,183,293,000		$ 12,183,293,000		$ 10,515,505,000
Interest income from related party	100,000	$ 100,000	200,000	$ 300,000
Gains on loans to related party	0	0	0	0
Write-down to fair value for loans sold to related party	1,500,000	1,500,000	3,600,000	3,700,000
Split Loans
Related Party Transaction [Line Items]
Split loans, net	76,000,000		76,000,000
Participated loans
Related Party Transaction [Line Items]
Loans sold to related party	$ 3,900,000	$ 5,900,000	$ 9,400,000	$ 14,600,000