NONINTEREST INCOME - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2018
Trust and investment services fees
Trailing commission income	$ 4	$ 12

Amount of revenue recognized arising from contract liability from change in timeframe for performance obligation to be satisfied.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130551-203045

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