Income Taxes - Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Student loans	$ 13,532	$ 20,980
Deferred revenue	3,246	2,699
Securitizations	2,970	5,675
Intangible assets	2,899	4,821
Accrued expenses	2,246	3,533
Stock compensation	1,744	2,948
Total gross deferred tax assets	26,637	40,656
Less valuation allowance	(254)	(264)
Net deferred tax assets	26,383	40,392
Deferred tax liabilities:
Basis in certain derivative contracts	23,051	46,636
Partnership basis	21,474	4,976
Loan origination services	8,001	13,019
Depreciation	4,958	5,128
Debt repurchases	3,856	12,457
Debt and equity investments	1,767	3,246
Other	823	360
Total gross deferred tax liabilities	63,930	85,822
Net deferred tax liability	$ (37,547)	$ (45,430)