CONSOLIDATED STATEMENTS OF INCOME - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest income:
Loans	$ 1,413,505	$ 1,060,487	$ 817,120
Investments	8,288	9,160	10,247
Cash and cash equivalents	15,510	7,599	3,751
Total interest income	1,437,303	1,077,246	831,118
Interest expense:
Deposits	223,691	148,408	116,391
Interest expense on short-term borrowings	6,341	7,322	6,490
Interest expense on long-term borrowings	78,050	30,178	5,738
Total interest expense	308,082	185,908	128,619
Net interest income	1,129,221	891,338	702,499
Less: provisions for credit losses	185,765	159,405	90,055
Net interest income after provisions for credit losses	943,456	731,933	612,444
Non-interest income (loss):
Gains on sales of loans, net	0	230	135,358
(Losses) gains on derivatives and hedging activities, net	(8,266)	(958)	5,300
Other income	5,364	69,544	41,935
Total non-interest income (loss)	(2,902)	68,816	182,593
Non-interest expenses:
Compensation and benefits	213,319	183,996	158,975
FDIC assessment fees	28,950	19,209	14,348
Other operating expenses	206,351	182,202	175,772
Total operating expenses	448,620	385,407	349,095
Acquired intangible asset amortization expense	469	906	1,480
Restructuring and other reorganization expenses	0	0	5,398
Total non-interest expenses	449,089	386,313	355,973
Income before income tax expense	491,465	414,436	439,064
Income tax expense	202,531	164,109	164,780
Net income	288,934	250,327	274,284
Preferred stock dividends	15,714	21,204	19,595
Net income attributable to SLM Corporation common stock	$ 273,220	$ 229,123	$ 254,689
Basic earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.63	$ 0.54	$ 0.60
Average common shares outstanding (in shares)	431,216	427,876	425,574
Diluted earnings per common share attributable to SLM Corporation (in dollars per share)	$ 0.62	$ 0.53	$ 0.59
Average common and common equivalent shares outstanding (in shares)	438,551	432,919	432,234