INVESTMENT SECURITIES - Schedule of Gains (Losses) on Investment and Trading Securities (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2026	Sep. 30, 2025	Sep. 30, 2026	Sep. 30, 2025
AFS debt and other securities:
Gross realized gains	$ 3	$ 0	$ 5	$ 0
Gross realized losses	(150)	0	(150)	0
Net realized losses on AFS and other securities	(147)	0	(145)	0
Total trading securities gains / (losses)	(17)	53	0	115
Total equity securities gains / (losses)	(12)	0	16	0
Securities gains / (losses), net	$ (176)	$ 53	$ (129)	$ 115

Amount of unrealized and realized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity), investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and investment in debt security measured at fair value with change in fair value recognized in net income (trading).

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(9)(a))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 220
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(7)(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483621/220-10-S99-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 944
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(3)(d))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477250/944-220-S99-1

Name:	us-gaap_DebtSecuritiesGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration