CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY (Unaudited) - USD ($)	Total	Series A Preferred Stock	Series B Preferred Stock	Navient's subsidiary investment	Preferred Stock	Common Stock	Treasury Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Retained Earnings Series A Preferred Stock	Retained Earnings Series B Preferred Stock	Total SLM Corporation Equity	Total SLM Corporation Equity Series A Preferred Stock	Total SLM Corporation Equity Series B Preferred Stock	Non-controlling interest
Beginning Balance (in shares) at Dec. 31, 2013					0	0	0
Beginning Balance, shares issued (in shares) at Dec. 31, 2013						0
Beginning Balance at Dec. 31, 2013	$ 1,166,143,000			$ 1,164,495,000	$ 0	$ 0	$ 0	$ 0	$ (3,024,000)	$ 0			$ 1,161,471,000			$ 4,672,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	91,142,000			68,173,000						23,403,000			91,576,000			(434,000)
Other comprehensive income (loss), net of tax	2,659,000								2,659,000				2,659,000
Comprehensive income	93,801,000												94,235,000			(434,000)
Net transfers (to) from affiliate	479,409,000			479,409,000									479,409,000
Separation adjustments related to Spin-Off of Navient Corporation (in shares)					7,300,000	422,790,320	0
Separation adjustments related to Spin-Off of Navient Corporation	0			(1,712,077,000)	$ 565,000,000	$ 84,558,000		1,062,519,000
Sale of non-controlling interest	(4,238,000)															(4,238,000)
Cash dividends:
Cash dividends, preferred stock		$ (1,917,000)	$ (1,311,000)								$ (1,917,000)	$ (1,311,000)		$ (1,917,000)	$ (1,311,000)
Dividend equivalent units related to employee stock-based compensation plans	$ 0							8,000		(8,000)
Issuance of common shares (in shares)	504,929					504,929
Issuance of common shares	$ 2,445,000					$ 101,000		2,344,000					2,445,000
Stock-based compensation expense	7,045,000							7,045,000					7,045,000
Shares repurchased related to employee stock-based compensation plans (in shares)						(358,771)	(358,771)
Shares repurchased related to employee stock-based compensation plans	(3,113,000)						$ (3,113,000)						(3,113,000)
Ending Balance (in shares) at Jun. 30, 2014					7,300,000	422,936,478	(358,771)
Ending Balance, shares issued (in shares) at Jun. 30, 2014						423,295,249
Ending Balance at Jun. 30, 2014	1,738,264,000			$ 0	$ 565,000,000	$ 84,659,000	$ (3,113,000)	1,071,916,000	(365,000)	20,167,000			1,738,264,000			$ 0
Beginning Balance (in shares) at Dec. 31, 2014					7,300,000	423,438,848	(1,365,277)
Beginning Balance, shares issued (in shares) at Dec. 31, 2014						424,804,125
Beginning Balance at Dec. 31, 2014	1,829,958,000				$ 565,000,000	$ 84,961,000	$ (12,187,000)	1,090,511,000	(11,393,000)	113,066,000			1,829,958,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	138,715,000									138,715,000			138,715,000
Other comprehensive income (loss), net of tax	(55,000)								(55,000)				(55,000)
Comprehensive income	138,660,000												138,660,000
Net transfers (to) from affiliate	$ 0
Cash dividends:
Cash dividends, preferred stock											$ (5,750,000)	$ (3,943,000)		$ (5,750,000)	$ (3,943,000)
Dividend equivalent units related to employee stock-based compensation plans								1,121,000		(1,121,000)			0
Issuance of common shares (in shares)	5,208,074					5,208,074
Issuance of common shares						$ 1,042,000		12,307,000					13,349,000
Tax benefit related to employee stock-based compensation								5,774,000					5,774,000
Stock-based compensation expense								11,210,000					11,210,000
Shares repurchased related to employee stock-based compensation plans (in shares)						(2,764,093)	(2,764,093)
Shares repurchased related to employee stock-based compensation plans							$ (27,085,000)						(27,085,000)
Ending Balance (in shares) at Jun. 30, 2015					7,300,000	425,882,829	(4,129,370)
Ending Balance, shares issued (in shares) at Jun. 30, 2015						430,012,199
Ending Balance at Jun. 30, 2015	$ 1,962,173,000				$ 565,000,000	$ 86,003,000	$ (39,272,000)	$ 1,120,923,000	$ (11,448,000)	$ 240,967,000			$ 1,962,173,000