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Segment Disclosures (Schedule of Segment Disclosures) (Details) - USD ($) $ in Millions	3 Months Ended								6 Months Ended		9 Months Ended		12 Months Ended
	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Segment Reporting Information [Line Items]
Interest income													$ 17,845	$ 12,864	$ 10,651
Interest expense													4,746	1,865	1,134
Net interest income													13,099	10,999	9,517
Provision for credit losses													6,018	2,359	218
Other income	$ 712	$ 705	$ 684	$ 594	$ 634	$ 606	$ 584	$ 393	$ 1,278	$ 977	$ 1,983	$ 1,583	2,695	2,217	2,490
Other expense	1,788	1,564			1,495	1,368					4,351	3,721	6,139	5,216	4,805
Income before income taxes	$ 483	$ 761	$ 1,152	$ 1,241	$ 1,323	$ 1,308	$ 1,422	$ 1,588	$ 2,393	$ 3,010	$ 3,154	$ 4,318	3,637	5,641	6,984
Credit Card Loans [Member]
Segment Reporting Information [Line Items]
Interest income													14,438	10,632	8,717
Total Other Loans [Member] \| Private Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income													1,033	831	742
Total Other Loans [Member] \| Personal Loans [Member]
Segment Reporting Information [Line Items]
Interest income													1,156	872	878
Total Other Loans [Member] \| Other Loans [Member]
Segment Reporting Information [Line Items]
Interest income													326	167	114
Unallocated Financing Receivables \| Other [Member]
Segment Reporting Information [Line Items]
Interest income													892	362	200
Operating Segments [Member] \| Digital Banking [Member]
Segment Reporting Information [Line Items]
Interest income													17,845	12,864	10,651
Interest expense													4,746	1,865	1,134
Net interest income													13,099	10,999	9,517
Provision for credit losses													6,018	2,359	218
Other income													2,245	2,041	1,701
Other expense													5,945	5,049	4,549
Income before income taxes													3,381	5,632	6,451
Operating Segments [Member] \| Digital Banking [Member] \| Credit Card Loans [Member]
Segment Reporting Information [Line Items]
Interest income													14,438	10,632	8,717
Operating Segments [Member] \| Digital Banking [Member] \| Total Other Loans [Member] \| Private Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income													1,033	831	742
Operating Segments [Member] \| Digital Banking [Member] \| Total Other Loans [Member] \| Personal Loans [Member]
Segment Reporting Information [Line Items]
Interest income													1,156	872	878
Operating Segments [Member] \| Digital Banking [Member] \| Total Other Loans [Member] \| Other Loans [Member]
Segment Reporting Information [Line Items]
Interest income													326	167	114
Operating Segments [Member] \| Digital Banking [Member] \| Unallocated Financing Receivables \| Other [Member]
Segment Reporting Information [Line Items]
Interest income													892	362	200
Operating Segments [Member] \| Payment Services [Member]
Segment Reporting Information [Line Items]
Interest income													0	0	0
Interest expense													0	0	0
Net interest income													0	0	0
Provision for credit losses													0	0	0
Other income													450	176	789
Other expense													194	167	256
Income before income taxes													256	9	533
Operating Segments [Member] \| Payment Services [Member] \| Credit Card Loans [Member]
Segment Reporting Information [Line Items]
Interest income													0	0	0
Operating Segments [Member] \| Payment Services [Member] \| Total Other Loans [Member] \| Private Student Loans [Member]
Segment Reporting Information [Line Items]
Interest income													0	0	0
Operating Segments [Member] \| Payment Services [Member] \| Total Other Loans [Member] \| Personal Loans [Member]
Segment Reporting Information [Line Items]
Interest income													0	0	0
Operating Segments [Member] \| Payment Services [Member] \| Total Other Loans [Member] \| Other Loans [Member]
Segment Reporting Information [Line Items]
Interest income													0	0	0
Operating Segments [Member] \| Payment Services [Member] \| Unallocated Financing Receivables \| Other [Member]
Segment Reporting Information [Line Items]
Interest income													$ 0	$ 0	$ 0