MORTGAGE BANKING AND OTHER SERVICED LOANS - Other Serviced Loans (Details) - USD ($) $ in Millions	Sep. 30, 2023	Dec. 31, 2022
Education
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other serviced loans	$ 517	$ 602
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Other serviced loans	$ 94	$ 91

Aggregate amount of servicing assets that are subsequently measured at fair value and servicing assets that are subsequently measured using the amortization method.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 50
-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147481260/860-50-45-2

Name:	us-gaap_ServicingAsset
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant