Arrangements with Navient Corporation (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 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	$ 12,021,022,000		$ 10,515,505,000
Interest income from related party	100,000	$ 200,000
Gains on loans to related party	0	0
Write-down to fair value for loans sold to related party	2,100,000	2,200,000
Split Loans
Related Party Transaction [Line Items]
Split loans, net	82,000,000
Participated loans
Related Party Transaction [Line Items]
Loans sold to related party	$ 5,500,000	$ 8,700,000