REDEEMABLE PREFERRED STOCK - Series L Preferred Stock (Details) - USD ($)				1 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 20, 2019	Nov. 20, 2019	Nov. 21, 2017	Nov. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Class of Stock [Line Items]
Redeemable preferred stock redemptions					$ 1,000	$ 0	$ 67,000	$ 8,000
Initial dividend on common stock	$ 4,380,645
Initial dividend, common stock, paid							$ 3,319,274	$ 12,045,000
Series L Preferred Stock
Class of Stock [Line Items]
Preferred stock, shares issued (in shares)			8,080,740		8,080,740		8,080,740		5,387,160
Preferred stock, liquidation preference per share (in usd per share)					$ 28.37		$ 28.37		$ 28.37
Cumulative dividend rate			5.50%
Preferred dividend per share per year (in usd per share)			$ 1.56035
Failure to declare or pay distributions, temporary increase per year			1.00%
Failure to declare or pay distributions, temporary increase per year, maximum increase			8.50%
Minimum fixed charge coverage ratio			125.00%
Series L Preferred Stock | Tender Offer
Class of Stock [Line Items]
Shares repurchased (in shares)				2,693,580
Purchase price (in usd per share)				$ 29.12
Preferred dividends declared (in usd per share)		$ 1.39
Dividends, preferred stock, aggregate value		$ 3,744,000
Professional fees				$ 462,000
Cost to repurchase tendered shares				$ 75,155,000
Redeemable preferred stock redemptions									$ 5,873,000
Series L Preferred Stock | Registration Statement
Class of Stock [Line Items]
Preferred stock, liquidation preference per share (in usd per share)			$ 28.37