REDEEMABLE PREFERRED STOCK (Details) - USD ($)					12 Months Ended
	Feb. 20, 2019	Jan. 03, 2018	Nov. 21, 2017	Apr. 22, 2016	Dec. 31, 2018	Dec. 31, 2017
Class of Stock [Line Items]
Deferred offering costs					$ 4,213,000	$ 3,401,000
Offering costs allocated to temporary equity					$ 29,304,000
Series A Preferred Stock
Class of Stock [Line Items]
Preferred stock redemption, trading days prior to redemption				20 days	20 days
Proceeds from issuance of preferred stock					$ 71,041,000
Offering costs					5,558,000
Deferred offering costs					4,568,000
Offering costs allocated to temporary equity					$ 354,000
Preferred stock, shares redeemed (in shares)		600			6,405
Cumulative dividend rate					5.50%
Preferred stock, dividend rate (in usd per share)					$ 0.34375
Preferred stock, shares issued (in shares)					1,566,386	1,225,734
Preferred stock, conversion amount per share (in usd per share)					$ 25.00	$ 25.00
Series A Preferred Stock | Subsequent event
Class of Stock [Line Items]
Preferred stock, dividends per share, declared (in usd per share)	$ 0.34375
Series A Preferred Stock | Preferred stock, redemption period, year two
Class of Stock [Line Items]
Preferred stock, redemption fee percentage				13.00%
Series A Preferred Stock | Preferred stock, redemption period, after year two, before year five
Class of Stock [Line Items]
Preferred stock, redemption fee percentage				10.00%
Series A Preferred Stock | Preferred stock, redemption period, after year five
Class of Stock [Line Items]
Preferred stock, redemption fee percentage				0.00%
Series A Preferred Unit
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)					2,853,555
Proceeds from issuance of preferred stock					$ 71,339,000
Offering costs					5,651,000
Warrant
Class of Stock [Line Items]
Proceeds from issuance of preferred stock					298,000
Offering costs					93,000
Offering costs allocated to temporary equity					$ 1,000
Series L Preferred Stock
Class of Stock [Line Items]
Proceeds from issuance of preferred stock			$ 229,251,000
Preferred stock, shares redeemed (in shares)					0
Cumulative dividend rate					5.50%
Preferred stock, dividend rate (in usd per share)					$ 1.56035
Preferred stock, shares issued (in shares)			8,080,740		8,080,740	8,080,740
Preferred stock, conversion amount per share (in usd per share)					$ 28.37	$ 23.87
Offering costs			$ 15,928,000
Discount on shares issued			2,946,000
Offering costs, non-issuance specific			$ 2,532,000
Dividend increase per year for failure to timely declare or pay dividends					1.00%
Dividend increase per year for failure to timely declare or pay dividends, maximum increase					8.50%
Minimum fixed charge coverage ratio					125.00%
Registration statement | Series A Preferred Stock
Class of Stock [Line Items]
Maximum amount of offering				$ 900,000,000
Preferred stock, par value (in usd per share)				$ 0.001
Preferred stock stated value (in usd per share)				$ 25.00
Warrant right to purchase a share of common stock (in shares)				0.25
Registration statement | Series A Preferred Unit
Class of Stock [Line Items]
Maximum number of units in offering (in shares)				36,000,000
Registration statement | Series L Preferred Stock
Class of Stock [Line Items]
Preferred stock, conversion amount per share (in usd per share)			$ 28.37