CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Interest income:
Loans	$ 1,756,945	$ 1,989,004	$ 2,249,169
Investments	13,859	11,743	7,607
Cash and cash equivalents	6,040	20,913	74,256
Total interest income	1,776,844	2,021,660	2,331,032
Interest expense:
Deposits	225,370	393,194	547,746
Interest expense on short-term borrowings	18,945	14,459	6,193
Interest expense on long-term borrowings	137,763	134,014	153,778
Total interest expense	382,078	541,667	707,717
Net interest income	1,394,766	1,479,993	1,623,315
Less: provisions for credit losses	(32,957)	93,133	354,249
Net interest income after provisions for credit losses	1,427,723	1,386,860	1,269,066
Non-interest income:
Gains on sales of loans, net	548,315	238,315	0
Gains on derivatives and hedging activities, net	144	49,544	17,825
Other income	83,990	43,590	31,102
Total non-interest income	632,449	331,449	48,927
Operating expenses
Compensation and benefits	258,321	282,497	278,229
FDIC assessment fees	23,368	21,956	32,852
Other operating expenses	236,964	233,635	263,172
Total operating expenses	518,653	538,088	574,253
Restructuring expenses	1,255	26,215	0
Total non-interest expenses	519,908	564,303	574,253
Income before income tax expense	1,540,264	1,154,006	743,740
Income tax expense	379,751	273,316	165,464
Net income	1,160,513	880,690	578,276
Preferred stock dividends	4,736	9,734	16,837
Net income attributable to SLM Corporation common stock	$ 1,155,777	$ 870,956	$ 561,439
Basic earnings per common share (in usd per share)	$ 3.67	$ 2.27	$ 1.31
Average common shares outstanding (in shares)	314,993	383,705	427,292
Diluted earnings per common share (in usd per share)	$ 3.61	$ 2.25	$ 1.30
Average common and common equivalent shares outstanding (in shares)	319,912	387,195	430,674
Declared dividends per common share (in usd per share)	$ 0.20	$ 0.12	$ 0.12