OFFSETTING OF ASSETS AND LIABILITIES - Narrative (Details) - USD ($)	Mar. 31, 2019	Dec. 31, 2018
Offsetting [Abstract]
Fair value of non-cash collateral received	$ 31,000,000	$ 45,000,000.0

Fair value of collateral permitted, by contact or custom, to be sold or re-pledged.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=109249958&loc=SL6224234-111729

Name:	us-gaap_FairValueOfSecuritiesReceivedAsCollateralThatCanBeResoldOrRepledged
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant