ORGANIZATION AND SIGNIFICANT ACCOUNTING POLICIES - Capital Raising Activities (Narrative) (Details) - USD ($)				3 Months Ended						6 Months Ended	9 Months Ended		11 Months Ended	12 Months Ended
	Oct. 29, 2021	Mar. 05, 2021	Jan. 25, 2021	Sep. 30, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Mar. 31, 2020	Aug. 03, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 21, 2021	Dec. 31, 2020
Subsidiary, Sale of Stock [Line Items]
Proceeds From Issuance Of Common Stock, net of issuance costs											$ 398,661,000	$ 35,013,000
Stock Issued During Period, Value, New Issues					$ 177,007,000	$ 124,746,000	$ 96,908,000	$ 15,566,000	$ 19,447,000		$ 398,661,000			$ 71,050,000
Total shares issued under distribution agreement					35,818,000	23,087,000	18,248,000	3,073,000	3,171,000		77,153,475			13,019,240
At the Market Offering Program [Member]
Subsidiary, Sale of Stock [Line Items]
Proceeds From Issuance Of Common Stock, net of issuance costs	$ 38,400,000			$ 207,500,000						$ 19,400,000			$ 147,400,000
Stock Issued During Period, Value, New Issues	$ 39,000,000.0			$ 211,000,000.0						$ 19,800,000			$ 150,000,000.0
Total shares issued under distribution agreement	7,838,998			41,568,338						3,170,727			27,493,650
At the Market Offering Program [Member] | Maximum [Member]
Subsidiary, Sale of Stock [Line Items]
Stock Issued During Period, Value, New Issues				$ 250,000,000						$ 200,000,000			$ 150,000,000
Follow-on Offering [Member]
Subsidiary, Sale of Stock [Line Items]
Proceeds From Issuance Of Common Stock, net of issuance costs		$ 50,000,000.0	$ 45,200,000
Total shares issued under distribution agreement		9,200,000	8,740,000
Share Price		$ 5.45	$ 5.20
Firm Offering Member [Member]
Subsidiary, Sale of Stock [Line Items]
Total shares issued under distribution agreement		8,000,000	7,600,000
Over-Allotment Option [Member]
Subsidiary, Sale of Stock [Line Items]
Total shares issued under distribution agreement		1,200,000	1,140,000,000