LOANS AND ALLOWANCE FOR CREDIT LOSSES - Schedule of Consumer Lending Asset Quality Indicators-Credit Score (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended	12 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025	Dec. 31, 2025
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total	$ 141,755		$ 141,755		$ 82,891
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total	1,198	$ 1,200	3,435	$ 3,477
Consumer
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Total	59,781		59,781		49,083
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Total	1,136	$ 1,163	3,323	$ 3,359
Consumer \| RICs and auto loans
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	14,896		14,896		15,956
Year Two	11,896		11,896		12,734
Year Three	8,943		8,943		6,677
Year Four	4,398		4,398		4,506
Year Five	2,640		2,640		1,955
Prior	1,261		1,261		908
Total	$ 44,034		$ 44,034		$ 42,736
Total, percent	100.00%		100.00%		100.00%
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current Fiscal Year			$ 156		$ 436
Year Two			1,095		1,606
Year Three			951		1,143
Year Four			573		776
Year Five			325		271
Prior			162		164
Total			3,262		4,396
Consumer \| RICs and auto loans \| No FICO
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 1,187		1,187		1,295
Year Two	846		846		787
Year Three	500		500		338
Year Four	215		215		238
Year Five	137		137		88
Prior	52		52		44
Total	$ 2,937		$ 2,937		$ 2,790
Total, percent	6.70%		6.70%		6.50%
Consumer \| RICs and auto loans \| Less than 600
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 5,854		$ 5,854		$ 6,495
Year Two	4,947		4,947		4,231
Year Three	2,991		2,991		2,372
Year Four	1,578		1,578		1,493
Year Five	892		892		614
Prior	424		424		348
Total	$ 16,686		$ 16,686		$ 15,553
Total, percent	37.80%		37.80%		36.40%
Consumer \| RICs and auto loans \| 600-639
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 2,452		$ 2,452		$ 3,189
Year Two	2,380		2,380		2,411
Year Three	1,684		1,684		1,374
Year Four	903		903		900
Year Five	536		536		303
Prior	194		194		126
Total	$ 8,149		$ 8,149		$ 8,303
Total, percent	18.50%		18.50%		19.40%
Consumer \| RICs and auto loans \| 640-679
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 1,369		$ 1,369		$ 1,867
Year Two	1,370		1,370		1,711
Year Three	1,193		1,193		864
Year Four	570		570		571
Year Five	340		340		176
Prior	114		114		70
Total	$ 4,956		$ 4,956		$ 5,259
Total, percent	11.30%		11.30%		12.30%
Consumer \| RICs and auto loans \| 680-719
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 940		$ 940		$ 1,130
Year Two	822		822		1,148
Year Three	802		802		645
Year Four	425		425		395
Year Five	233		233		172
Prior	119		119		85
Total	$ 3,341		$ 3,341		$ 3,575
Total, percent	7.60%		7.60%		8.40%
Consumer \| RICs and auto loans \| 720-759
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 580		$ 580		$ 616
Year Two	458		458		739
Year Three	524		524		418
Year Four	277		277		293
Year Five	169		169		166
Prior	109		109		75
Total	$ 2,117		$ 2,117		$ 2,307
Total, percent	4.80%		4.80%		5.40%
Consumer \| RICs and auto loans \| >=760
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 2,514		$ 2,514		$ 1,364
Year Two	1,073		1,073		1,707
Year Three	1,249		1,249		666
Year Four	430		430		616
Year Five	333		333		436
Prior	249		249		160
Total	$ 5,848		$ 5,848		$ 4,949
Total, percent	13.30%		13.30%		11.60%
Consumer \| Personal unsecured loans
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 62		$ 62		$ 70
Year Two	56		56		59
Year Three	50		50		66
Year Four	52		52		65
Year Five	50		50		21
Prior	236		236		211
Total	$ 506		$ 506		$ 492
Total, percent	100.00%		100.00%		100.00%
Financing Receivable, Excluding Accrued Interest, Allowance for Credit Loss, Writeoff, by Origination Year [Abstract]
Current Fiscal Year			$ 0		$ 7
Year Two			7		38
Year Three			13		68
Year Four			13		31
Year Five			7		6
Prior			10		15
Total			50		165
Consumer \| Personal unsecured loans \| No FICO
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 24		24		13
Year Two	3		3		0
Year Three	4		4		0
Year Four	1		1		0
Year Five	0		0		0
Prior	2		2		0
Total	$ 34		$ 34		$ 13
Total, percent	6.70%		6.70%		2.60%
Consumer \| Personal unsecured loans \| Less than 600
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 0		$ 0		$ 0
Year Two	0		0		0
Year Three	0		0		0
Year Four	0		0		0
Year Five	0		0		0
Prior	4		4		3
Total	$ 4		$ 4		$ 3
Total, percent	0.80%		0.80%		0.60%
Consumer \| Personal unsecured loans \| 600-639
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 1		$ 1		$ 1
Year Two	1		1		1
Year Three	1		1		1
Year Four	1		1		1
Year Five	1		1		0
Prior	4		4		5
Total	$ 9		$ 9		$ 9
Total, percent	1.80%		1.80%		1.80%
Consumer \| Personal unsecured loans \| 640-679
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 3		$ 3		$ 3
Year Two	4		4		5
Year Three	4		4		7
Year Four	5		5		7
Year Five	5		5		2
Prior	28		28		27
Total	$ 49		$ 49		$ 51
Total, percent	9.70%		9.70%		10.40%
Consumer \| Personal unsecured loans \| 680-719
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 6		$ 6		$ 11
Year Two	11		11		16
Year Three	11		11		20
Year Four	14		14		16
Year Five	12		12		5
Prior	59		59		57
Total	$ 113		$ 113		$ 125
Total, percent	22.30%		22.30%		25.40%
Consumer \| Personal unsecured loans \| 720-759
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 10		$ 10		$ 16
Year Two	15		15		17
Year Three	13		13		21
Year Four	15		15		22
Year Five	16		16		7
Prior	60		60		57
Total	$ 129		$ 129		$ 140
Total, percent	25.50%		25.50%		28.50%
Consumer \| Personal unsecured loans \| >=760
Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, by Origination Year [Abstract]
Current Fiscal Year	$ 18		$ 18		$ 26
Year Two	22		22		20
Year Three	17		17		17
Year Four	16		16		19
Year Five	16		16		7
Prior	79		79		62
Total	$ 168		$ 168		$ 151
Total, percent	33.20%		33.20%		30.60%

Financing Receivable, Excluding Accrued Interest, before Allowance for Credit Loss, Excluding Loans Held For Sale

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Financing Receivable, Excluding Accrued Interest, Before Allowance for Credit Loss, Percent

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Financing Receivable, Excluding Accrued Interest, Originated, More than Five Years before Current Fiscal Year, Excluding Loans Held for Sale

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Financing Receivable, Excluding Accrued Interest, Year Five, Originated, Four Years before Current Fiscal Year, Excluding Loans Held for Sale

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Financing Receivable, Excluding Accrued Interest, Year Four, Originated, Three Years before Current Fiscal Year, Excluding Loans Held for Sale

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Financing Receivable, Excluding Accrued Interest, Year One, Originated, Current Fiscal Year, Excluding Loans Held for Sale

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Financing Receivable, Excluding Accrued Interest, Year Three, Originated, Two Years before Current Fiscal Year, Excluding Loans Held for Sale

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Financing Receivable, Excluding Accrued Interest, Year Two, Originated, Fiscal Year before Current Fiscal Year, Excluding Loans Held for Sale

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Amount, excluding accrued interest, of decrease in allowance for credit loss on financing receivable from writeoff. Excludes net investment in lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 13
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-13

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

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Amount, excluding accrued interest, of writeoff of financing receivable originated more than five years before current fiscal year. Excludes net investment in lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 326
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-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479319/326-20-50-6

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Amount, excluding accrued interest, of writeoff of financing receivable originated four years before current fiscal year. Excludes net investment in lease.

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Amount, excluding accrued interest, of writeoff of financing receivable originated three years before current fiscal year. Excludes net investment in lease.

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Amount, excluding accrued interest, of writeoff of financing receivable originated in current fiscal year. Excludes net investment in lease.

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Amount, excluding accrued interest, of writeoff of financing receivable originated two years before current fiscal year. Excludes net investment in lease.

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