Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Operating activities
Net income	$ 228	$ 645	$ 717
Adjustments to reconcile net income to net cash provided by operating activities:
Gains on sale of education loans	0	0	(78)
Losses on debt repurchases	8	0	73
Goodwill and acquired intangible asset impairment and amortization expense	10	19	30
Stock-based compensation expense	24	19	22
Mark-to-market (gains)/losses on derivative and hedging activities, net	147	(590)	(433)
Provisions for loan losses	123	79	(61)
(Increase) decrease in accrued interest receivable	(50)	(147)	47
Increase (decrease) in accrued interest payable	29	159	(55)
Decrease in other assets	52	387	145
Increase (decrease) in other liabilities	105	(266)	295
Total adjustments	448	(340)	(15)
Total net cash provided by operating activities	676	305	702
Investing activities
Education loans originated and acquired	(970)	(2,051)	(6,104)
Principal payments on education loans	8,322	12,540	11,137
Proceeds from sales of education loans	0	0	1,588
Other investing activities, net	5	96	68
Purchase of subsidiary, net of cash acquired	0	0	(16)
Total net cash provided by investing activities	7,357	10,585	6,673
Financing activities
Borrowings collateralized by loans in trust - issued	1,357	2,243	7,973
Borrowings collateralized by loans in trust - repaid	(9,753)	(12,581)	(11,163)
Long-term unsecured notes issued	989	0	1,237
Long-term unsecured notes repaid	(2,159)	(15)	(2,702)
Other financing activities, net	(101)	89	197
Common stock repurchased	(310)	(400)	(600)
Common dividends paid	(78)	(91)	(107)
Total net cash used in financing activities	(10,047)	(9,661)	(7,334)
Net increase (decrease) in cash, cash equivalents, restricted cash and restricted cash equivalents	(2,014)	1,229	41
Cash, cash equivalents, restricted cash and restricted cash equivalents at beginning of period	4,807	3,578	3,537
Cash, cash equivalents, restricted cash and restricted cash equivalents at end of period	2,793	4,807	3,578
Cash disbursements made (refunds received) for:
Interest	3,431	1,904	1,378
Income taxes paid	57	30	190
Income taxes received	(5)	(12)	(11)
Reconciliation of the Consolidated Statements of Cash Flows to the Consolidated Balance Sheets:
Cash and cash equivalents	839	1,535	905
Restricted cash and restricted cash equivalents	1,954	3,272	2,673
Total cash, cash equivalents, restricted cash and restricted cash equivalents at end of period	2,793	4,807	3,578
Non-cash activities
Investing activity - Held-to-maturity asset backed securities retained related to sales of education loans	0	0	83
Operating activity - Servicing assets recognized upon sales of education loans	0	0	21
Asset-backed Securities, Securitized Loans and Receivables [Member]
Financing activities
Asset-backed commercial paper conduits, net	$ 8	$ 1,094	$ (2,169)