CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Interest income:
Loans	$ 2,327,743	$ 1,914,554	$ 1,756,945
Investments	50,810	35,304	13,859
Cash and cash equivalents	213,750	81,722	6,040
Total interest income	2,592,303	2,031,580	1,776,844
Interest expense:
Deposits	808,065	368,914	225,370
Interest expense on short-term borrowings	13,501	11,956	18,945
Interest expense on long-term borrowings	208,524	161,929	137,763
Total interest expense	1,030,090	542,799	382,078
Net interest income	1,562,213	1,488,781	1,394,766
Less: provisions for credit losses	345,463	633,453	(32,957)
Net interest income after provisions for credit losses	1,216,750	855,328	1,427,723
Non-interest income:
Gains on sales of loans, net	160,290	327,750	548,315
Gains (losses) on securities, net	2,678	(60,267)	39,096
Gains (losses) on derivatives and hedging activities, net	0	(5)	144
Other income	84,148	67,160	44,894
Total non-interest income	247,116	334,638	632,449
Operating expenses:
Compensation and benefits	326,554	270,354	258,321
FDIC assessment fees	45,766	20,939	23,368
Other operating expenses	246,886	260,169	236,964
Total operating expenses	619,206	551,462	518,653
Amortized intangible assets	66,364	7,779	0
Restructuring expenses	0	0	1,255
Total non-interest expenses	685,570	559,241	519,908
Income before income tax expense	778,296	630,725	1,540,264
Income tax expense	196,905	161,711	379,751
Net income	581,391	469,014	1,160,513
Preferred stock dividends	17,705	9,029	4,736
Net income attributable to SLM Corporation common stock	$ 563,686	$ 459,985	$ 1,155,777
Basic earnings per common share (in usd per share)	$ 2.44	$ 1.78	$ 3.67
Average common shares outstanding (in shares)	231,411	258,439	314,993
Diluted earnings per common share (in usd per share)	$ 2.41	$ 1.76	$ 3.61
Average common and common equivalent shares outstanding (in shares)	234,063	261,503	319,912
Declared dividends per common share (in usd per share)	$ 0.44	$ 0.44	$ 0.20