SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Recently Issued Accounting Update (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 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	9,400	9,400
Variable lease revenue	4,000	13,000
Variable lease expense	$ 4,000	$ 13,000
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