SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Noncontrolling Interests in Consolidated Entities (Details)	3 Months Ended	12 Months Ended
Mar. 31, 2018	Dec. 31, 2015
Class of Stock [Line Items]
Percentage of carried interest received by general partners (up to)		1.00%
Series A LLC Preferred Stock
Class of Stock [Line Items]
Preferred units dividend rate (as a percent)	7.375%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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