SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recently Issued Accounting Update (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability	$ 10,000
Operating lease right-of-use asset	9,800
Variable lease revenue	4,200
Variable lease expense	$ 4,200
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability		$ 10,000
Operating lease right-of-use asset		10,000
Reduction to equity and accounts receivable, prepaid expenses and other assets, net, as of the date of adoption		32,502
Straight-line rental income receivables		17,500
Cash rent receivable		$ 15,000