SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recently Issued Accounting Update (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease liability	$ 9,800	$ 9,800
Operating lease right-of-use asset	9,500	9,500
Variable lease revenue	4,800	9,000
Variable lease expense	$ 4,800	$ 9,000
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