Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Numerator:
Net income	$ 289,931	$ 118,518
Preferred stock dividends	4,653	4,063
Net income attributable to SLM Corporation common stock	285,278	114,455
Net income attributable to SLM Corporation common stock	$ 285,278	$ 114,455
Denominator:
Weighted average shares used to compute basic EPS (in shares)	220,416	241,497
Effect of dilutive securities:
Dilutive effect of stock options, restricted stock, restricted stock units and Employee Stock Purchase Plan (ESPP) (in shares)	3,429	2,052
Weighted average shares used to compute diluted EPS (in shares)	223,845	243,549
Basic earnings per common share (in dollars per share)	$ 1.29	$ 0.47
Diluted earnings per common share (in dollars per share)	$ 1.27	$ 0.47
Antidilutive securities excluded from computation of earnings per share (in shares)	2,000	4,000