Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Numerator:
Net income	$ 118,518	$ 128,812
Preferred stock dividends	4,063	1,275
Net income attributable to SLM Corporation common stock	114,455	127,537
Net income attributable to SLM Corporation common stock	$ 114,455	$ 127,537
Denominator:
Weighted average shares used to compute basic EPS (in shares)	241,497	276,977
Effect of dilutive securities:
Dilutive effect of stock options, restricted stock, restricted stock units and Employee Stock Purchase Plan (ESPP) (in shares)	2,052	3,677
Weighted average shares used to compute diluted EPS (in shares)	243,549	280,654
Basic earnings per common share (in dollars per share)	$ 0.47	$ 0.46
Diluted earnings per common share (in dollars per share)	$ 0.47	$ 0.45
Antidilutive securities excluded from computation of earnings per share (in shares)	4,000	3,000