Parent Only Statements - Balance Sheets (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Assets
Cash and cash equivalents	$ 2,416,219	$ 2,359,780	$ 2,182,865	$ 1,599,082
Tax indemnification receivable	186,076	240,311
Other assets	55,482	64,757
Total assets	15,214,098	12,972,243
Liabilities
Income taxes payable, net	166,662	191,499
Other liabilities	108,746	117,227
Total liabilities	13,117,775	11,142,285
Preferred stock, par value $0.20 per share, 20 million shares authorized
Common stock, par value $0.20 per share, 1.125 billion shares authorized: 430.7 million and 424.8 million shares issued, respectively	86,136	84,961
Additional paid-in capital	1,135,860	1,090,511
Accumulated other comprehensive loss (net of tax benefit of $9,949 and $7,186, respectively	(16,059)	(11,393)
Retained earnings	366,609	113,066
Total SLM Corporation's stockholders' equity before treasury stock	2,137,546	1,842,145
Less: common stock held in treasury at cost: 4.4 million and 1.4 million shares, respectively	(41,223)	(12,187)
Total liabilities and equity	15,214,098	12,972,243
Parent Company
Assets
Cash and cash equivalents	282,036	434,245	$ 0	$ 0
Total investments in subsidiaries (primarily Sallie Mae Bank)	1,810,567	1,389,995
Tax indemnification receivable	186,076	240,311
Due from subsidiaries, net	21,396	32,408
Other assets	1,352	1,943
Total assets	2,301,427	2,098,902
Liabilities
Income taxes payable, net	189,215	245,782
Payable due to Navient	1,990	8,764
Other liabilities	13,899	14,398
Total liabilities	205,104	268,944
Preferred stock, par value $0.20 per share, 20 million shares authorized
Common stock, par value $0.20 per share, 1.125 billion shares authorized: 430.7 million and 424.8 million shares issued, respectively	86,136	84,961
Additional paid-in capital	1,135,860	1,090,511
Accumulated other comprehensive loss (net of tax benefit of $9,949 and $7,186, respectively	(16,059)	(11,393)
Retained earnings	366,609	113,066
Total SLM Corporation's stockholders' equity before treasury stock	2,137,546	1,842,145
Less: common stock held in treasury at cost: 4.4 million and 1.4 million shares, respectively	(41,223)	(12,187)
Total SLM Corporation stockholders' equity	2,096,323	1,829,958
Total liabilities and equity	2,301,427	2,098,902
Parent Company | Series A Preferred Stock
Preferred stock, par value $0.20 per share, 20 million shares authorized
Preferred stock issued	165,000	165,000
Parent Company | Series B Preferred Stock
Preferred stock, par value $0.20 per share, 20 million shares authorized
Preferred stock issued	$ 400,000	$ 400,000