VARIABLE INTEREST ENTITIES - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
LIHTC Investments
Variable Interest Entity
Net impairment losses recognized in earnings	$ 0	$ 0

Amount of write-down from impairment of an investment in a qualified affordable housing project.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 740
-Section 50
-Paragraph 2
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=64813897&loc=SL49122993-202985

Name:	us-gaap_AffordableHousingProjectInvestmentWriteDownAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration