ORGANIZATION - Narrative (Details) - segment	3 Months Ended	12 Months Ended
Mar. 31, 2020	Dec. 31, 2019
Organization Basis Of Presentation [Line Items]
Number of reportable segments	4
Alliance Bernstein
Organization Basis Of Presentation [Line Items]
Economic interest	65.00%	65.00%

Number of segments reported by the entity. A reportable segment is a component of an entity for which there is an accounting requirement to report separate financial information on that component in the entity's financial statements.

No definition available.

Name:	us-gaap_NumberOfReportableSegments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration