CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Preferred Stock	Treasury Stock	Common Stock	Accumulated Other Comprehensive Income (Loss)	Additional Paid-in Capital	Additional Paid-in Capital Navient's Subsidiary Investment	Retained Earnings	Total SLM Corporation Equity	Non-controlling interest	Series A Preferred Stock	Series A Preferred Stock Retained Earnings	Series A Preferred Stock Total SLM Corporation Equity	Series B Preferred Stock	Series B Preferred Stock Retained Earnings	Series B Preferred Stock Total SLM Corporation Equity
Beginning balance at Dec. 31, 2012	$ 1,089,300				$ 14,348		$ 1,068,928		$ 1,083,276	$ 6,024
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	257,593				0		258,945		258,945	(1,352)
Other comprehensive loss, net of tax	(17,372)				(17,372)		0		(17,372)	0
Comprehensive income	240,221								241,573	(1,352)
Net transfers from affiliate	$ (163,378)				0		(163,378)		(163,378)	0
Cash dividends:
Issuance of common shares (in shares)	9,702,976
Ending balance, shares issued (in shares) at Dec. 31, 2013		0		0
Ending balance (in shares) at Dec. 31, 2013			0	0
Ending balance at Dec. 31, 2013	$ 1,166,143	$ 0	$ 0	$ 0	(3,024)	$ 0	1,164,495	$ 0	1,161,471	4,672
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	193,785						68,173	126,046	194,219	(434)
Other comprehensive loss, net of tax	(8,369)				(8,369)				(8,369)
Comprehensive income	185,416								185,850	(434)
Net transfers from affiliate	479,409						479,409		479,409
Separation adjustments related to Spin-Off of Navient Corporation (in shares)		7,300,000	0	422,790,320
Separation adjustments related to Spin-Off of Navient Corporation	0	$ 565,000		$ 84,558		1,062,519	(1,712,077)
Sale of non-controlling interest	(4,238)									(4,238)
Cash dividends:
Preferred stock											$ (7,667)	$ (7,667)	$ (7,667)	$ (5,266)	$ (5,266)	$ (5,266)
Dividend equivalent units related to employee stock-based compensation plans	$ 0					47		(47)
Issuance of common shares (in shares)	2,013,805			2,013,805
Issuance of common shares	$ 8,683			$ 403		8,280			8,683
Tax benefit related to employee stock-based compensation	3,271					3,271			3,271
Stock-based compensation expense	16,394					16,394			16,394
Shares repurchased related to employee stock-based compensation plans (in shares)			(1,365,277)	(1,365,277)
Shares repurchased related to employee stock-based compensation plans	(12,187)		$ (12,187)						(12,187)
Ending balance, shares issued (in shares) at Dec. 31, 2014		7,300,000		424,804,125
Ending balance (in shares) at Dec. 31, 2014			(1,365,277)	423,438,848
Ending balance at Dec. 31, 2014	1,829,958	$ 565,000	$ (12,187)	$ 84,961	(11,393)	1,090,511	$ 0	113,066	1,829,958	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	274,284							274,284	274,284
Other comprehensive loss, net of tax	(4,666)				(4,666)				(4,666)
Comprehensive income	$ 269,618								269,618
Separation adjustments related to Spin-Off of Navient Corporation						1,660			1,660
Cash dividends:
Preferred stock											$ (11,501)	$ (11,501)		$ (8,094)	$ (8,094)
Dividend equivalent units related to employee stock-based compensation plans						1,146		(1,146)	0
Issuance of common shares (in shares)	5,873,309			5,873,309
Issuance of common shares				$ 1,175		14,805			15,980
Tax benefit related to employee stock-based compensation						6,140			6,140
Stock-based compensation expense						21,598			21,598
Shares repurchased related to employee stock-based compensation plans (in shares)			(3,008,913)	(3,008,913)
Shares repurchased related to employee stock-based compensation plans			$ (29,036)						(29,036)
Ending balance, shares issued (in shares) at Dec. 31, 2015		7,300,000		430,677,434
Ending balance (in shares) at Dec. 31, 2015			(4,374,190)	426,303,244
Ending balance at Dec. 31, 2015	$ 2,096,323	$ 565,000	$ (41,223)	$ 86,136	$ (16,059)	$ 1,135,860		$ 366,609	$ 2,096,323