Business Segments and Revenue from Contracts with Customers - Segment Results and Reconciliation (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Segment Reporting Information [Line Items]
Net interest income (loss)	$ 7,423	$ 7,003	$ 21,722	$ 19,917
Non-interest income	1,943	1,802	5,559	5,293
Total net revenue (loss)	9,366	8,805	27,281	25,210
Change in estimated partner reimbursements that decreased/(increased) provision for credit losses	2,284	1,669	7,569	3,431
Non-interest expense	4,860	4,949	14,599	14,083
Loss from continuing operations before income taxes	2,222	2,187	5,113	7,696
Income tax provision (benefit)	432	493	932	1,568
Income (loss) from continuing operations, net of tax	1,790	1,694	4,181	6,128
Total loans held for investment	314,780	303,943	314,780	303,943	$ 312,331
Total Deposits	346,011	317,193	346,011	317,193	$ 332,992
Uncollectible portion of billed finance charges and fees	449	222	1,300	625
Operating segments | Credit Card
Segment Reporting Information [Line Items]
Net interest income (loss)	5,114	4,313	14,498	12,051
Non-interest income	1,513	1,454	4,375	4,322
Total net revenue (loss)	6,627	5,767	18,873	16,373
Change in estimated partner reimbursements that decreased/(increased) provision for credit losses	1,953	1,261	6,298	2,387
Non-interest expense	3,015	3,004	9,073	8,558
Loss from continuing operations before income taxes	1,659	1,502	3,502	5,428
Income tax provision (benefit)	393	356	830	1,291
Income (loss) from continuing operations, net of tax	1,266	1,146	2,672	4,137
Total loans held for investment	146,783	126,913	146,783	126,913
Total Deposits	0	0	0	0
Operating segments | Consumer Banking
Segment Reporting Information [Line Items]
Net interest income (loss)	2,133	2,311	6,762	6,571
Non-interest income	142	129	426	330
Total net revenue (loss)	2,275	2,440	7,188	6,901
Change in estimated partner reimbursements that decreased/(increased) provision for credit losses	213	285	747	696
Non-interest expense	1,262	1,340	3,776	3,862
Loss from continuing operations before income taxes	800	815	2,665	2,343
Income tax provision (benefit)	189	193	629	555
Income (loss) from continuing operations, net of tax	611	622	2,036	1,788
Total loans held for investment	76,844	81,199	76,844	81,199
Total Deposits	290,789	256,661	290,789	256,661
Operating segments | Commercial Banking
Segment Reporting Information [Line Items]
Net interest income (loss)	621	699	1,901	1,941
Non-interest income	288	319	757	868
Total net revenue (loss)	909	1,018	2,658	2,809
Change in estimated partner reimbursements that decreased/(increased) provision for credit losses	116	123	521	353
Non-interest expense	512	542	1,524	1,515
Loss from continuing operations before income taxes	281	353	613	941
Income tax provision (benefit)	67	83	145	223
Income (loss) from continuing operations, net of tax	214	270	468	718
Total loans held for investment	91,153	95,831	91,153	95,831
Total Deposits	36,035	41,058	36,035	41,058
Other
Segment Reporting Information [Line Items]
Net interest income (loss)	(445)	(320)	(1,439)	(646)
Non-interest income	0	(100)	1	(227)
Total net revenue (loss)	(445)	(420)	(1,438)	(873)
Change in estimated partner reimbursements that decreased/(increased) provision for credit losses	2	0	3	(5)
Non-interest expense	71	63	226	148
Loss from continuing operations before income taxes	(518)	(483)	(1,667)	(1,016)
Income tax provision (benefit)	(217)	(139)	(672)	(501)
Income (loss) from continuing operations, net of tax	(301)	(344)	(995)	(515)
Total loans held for investment	0	0	0	0
Total Deposits	$ 19,187	$ 19,474	$ 19,187	$ 19,474