Defined Contribution Plans (Details) - Sallie Mae 401(k) Savings Plan - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Contribution Plan Disclosure [Line Items]
Requisite service period	6 months	1 month
Type 1 of defined benefit contribution (up to)		3.00%
Type 2 of defined contribution plan		2.00%
Percent of core employer contribution		1.00%
Employer contribution amount		$ 4.4	$ 3.8	$ 3.1
Maximum
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution percentage		100.00%
Minimum
Defined Contribution Plan Disclosure [Line Items]
Employer matching contribution percentage		50.00%