Jernigan Capital (JCAP) 10-Q 9 Nov 20 2020 Q3 Quarterly report Financial data

Document And Entity Information

Document And Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 05, 2020
Document Type	10-Q
Document Quarterly Report	true
Document Transition Report	false
Amendment Flag	false
Entity Central Index Key	0001622353
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity File Number	001-36892
Entity Registrant Name	Jernigan Capital, Inc.
Entity Incorporation, State or Country Code	MD
Entity Tax Identification Number	47-1978772
Entity Address, Address Line One	6410 Poplar Avenue
Entity Address, Address Line Two	Suite 650
Entity Address, City or Town	Memphis
Entity Address, State or Province	TN
Entity Address, Postal Zip Code	38119
City Area Code	901
Local Phone Number	567-9510
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	true
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		23,263,130
Common Stock Class [Member]
Title of 12(b) Security	Common stock, par value $0.01 per share
Trading Symbol	JCAP
Security Exchange Name	NYSE
Series B Preferred Stock [Member]
Title of 12(b) Security	7.00% Series B cumulative redeemable perpetual preferred stock, $0.01 par value per share
Trading Symbol	JCAP PR B
Security Exchange Name	NYSE

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Assets:
Cash and cash equivalents	$ 22,183	$ 3,278
Development property investments at fair value	316,254	549,684
Self-storage real estate owned, net	513,993	230,844
Investment in and advances to self-storage real estate venture	4,053	11,247
Other loans, at cost	850	4,713
Deferred financing costs	7,717	4,154
Prepaid expenses and other assets	9,107	8,654
Fixed assets, net	127	203
Total assets	874,284	812,777
Liabilities:
Secured revolving credit facility	242,000	162,000
Term loans, net of unamortized costs	40,973	40,791
Due to Manager	0	3,164
Accounts payable, accrued expenses and other liabilities	13,388	4,817
Dividends payable	5,309	13,131
Total liabilities	301,670	223,903
Equity:
Common stock, $0.01 par value, 500,000,000 shares authorized at September 30, 2020 and December 31, 2019; 23,263,130 and 22,423,283 issued and outstanding at September 30, 2020 and December 31, 2019, respectively	232	224
Additional paid-in capital	451,182	426,129
Accumulated deficit	(89,289)	(5,021)
Accumulated other comprehensive income (loss)	(1,084)	(393)
Total Jernigan Capital, Inc. stockholders' equity	535,351	588,874
Non-controlling interests	37,263	0
Total equity	572,614	588,874
Total liabilities and equity	874,284	812,777
Series A Preferred Stock [Member]
Equity:
Preferred stock	137,012	130,637
Total equity	137,012	130,637
Series B Preferred Stock [Member]
Equity:
Preferred stock	37,298	37,298
Total equity	$ 37,298	$ 37,298

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	23,263,130	22,423,283
Common stock, shares outstanding	23,263,130	22,423,283
Series A Preferred Stock [Member]
Preferred stock, dividend rate	7.00%	7.00%
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	300,000	300,000
Preferred stock, shares issued	139,875	133,500
Preferred stock, shares outstanding	139,875	133,500
Preferred stock, liquidation preference, value	$ 139.9	$ 133.5
Series B Preferred Stock [Member]
Preferred stock, dividend rate	7.00%	7.00%
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	3,750,000	3,750,000
Preferred stock, shares issued	1,571,734	1,571,734
Preferred stock, shares outstanding	1,571,734	1,571,734
Preferred stock, liquidation preference, value	$ 39.3	$ 39.3

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenues:
Interest income from investments	$ 5,553	$ 10,216	$ 20,117	$ 27,578
Total revenues	11,878	12,249	35,242	32,965
Costs and expenses:
General and administrative expenses	2,592	2,137	8,817	6,273
Fees to Manager	0	2,131	1,230	6,203
Property operating expenses of real estate owned	3,781	989	8,454	2,538
Depreciation and amortization of real estate owned	5,414	1,372	13,319	3,491
Goodwill impairment loss	0	0	4,738	0
Total costs and expenses	16,828	6,897	79,387	18,773
Operating income (loss)	(4,950)	5,352	(44,145)	14,192
Other income (expense):
Equity in earnings (losses) from unconsolidated real estate venture	(2,041)	165	(2,195)	407
Net unrealized gain (loss) on investments	4,540	7,974	(5,630)	28,847
Interest expense	(3,196)	(2,546)	(9,475)	(5,535)
Other interest income	16	9	38	30
Total other income (loss)	(681)	5,602	(17,262)	23,749
Net income (loss)	(5,631)	10,954	(61,407)	37,941
Net income attributable to preferred stockholders	(5,309)	(5,157)	(15,760)	(15,283)
Less: Net loss attributable to non-controlling interests	1,005	0	3,604	0
Net income (loss) attributable to common stockholders	$ (9,935)	$ 5,797	$ (73,563)	$ 22,658
Basic earnings (loss) per share attributable to common stockholders	$ (0.43)	$ 0.26	$ (3.20)	$ 1.06
Diluted earnings (loss) per share attributable to common stockholders	(0.43)	0.26	(3.20)	1.06
Dividends declared per share of common stock	$ 0	$ 0.35	$ 0.46	$ 1.05
Rental and other property-related income from real estate owned [Member]
Revenues:
Revenues	$ 6,287	$ 1,988	$ 14,982	$ 5,075
Other revenues [Member]
Revenues:
Revenues	38	45	143	312
Internalization Expenses [Member]
Costs and expenses:
Other expenses	10	268	37,798	268
Merger Expenses [Member]
Costs and expenses:
Other expenses	$ 5,031	$ 0	$ 5,031	$ 0

CONSOLIDATED STATEMENTS OF OTHE

CONSOLIDATED STATEMENTS OF OTHER COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
CONSOLIDATED STATEMENTS OF OTHER COMPREHENSIVE INCOME [Abstract]
Net income (loss)	$ (5,631)	$ 10,954	$ (61,407)	$ 37,941
Other comprehensive income (loss):
Unrealized gains (losses) on interest rate swaps	(59)	(58)	(1,216)	(495)
Reclassification of realized losses (gains) on interest rate swaps	262	(1)	501	(5)
Other comprehensive income (loss)	203	(59)	(715)	(500)
Comprehensive income (loss)	(5,428)	10,895	(62,122)	37,441
Less: Net loss attributable to non-controlling interests	1,005	0	3,604	0
Less: Other comprehensive loss attributable to non-controlling interest	(18)	0	25	0
Comprehensive income (loss) attributable to common stockholders	$ (4,441)	$ 10,895	$ (58,493)	$ 37,441

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($) $ in Thousands	Series A Preferred Stock [Member]Total Stockholders' Equity [Member]	Series A Preferred Stock [Member]Retained Earnings (Accumulated Deficit) [Member]	Series A Preferred Stock [Member]	Series B Preferred Stock [Member]Total Stockholders' Equity [Member]	Series B Preferred Stock [Member]Retained Earnings (Accumulated Deficit) [Member]	Series B Preferred Stock [Member]	Total Stockholders' Equity [Member]Internalization Expenses [Member]	Total Stockholders' Equity [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]Internalization Expenses [Member]	Additional Paid-in Capital [Member]	Retained Earnings (Accumulated Deficit) [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-Controlling Interests [Member]Property Acquisition [Member]	Non-Controlling Interests [Member]Internalization Expenses [Member]	Non-Controlling Interests [Member]	Property Acquisition [Member]	Internalization Expenses [Member]	Total
Balance at Dec. 31, 2018			$ 122,137			$ 37,401		$ 547,864	$ 204		$ 386,394	$ 1,728							$ 547,864
Balance (in shares) at Dec. 31, 2018			125,000			1,571,734			20,430,218
Equity offering costs related to preferred stock costs						$ (103)		(103)											(103)
At-the-market issuance of common stock, net of offering costs								2,752	$ 1		2,751								2,752
At-the-market issuance of common stock, net of offering costs (in shares)									136,192
Stock dividend paid on preferred stock			$ 2,125					2,125											2,125
Stock dividend paid on preferred stock (in shares)			2,125
Repurchase and retirement of shares of common stock								(73)			(73)								(73)
Repurchase and retirement of shares of common stock (in shares)									(3,408)
Issuances of stock-based awards (in shares)									4,692
Stock-based compensation								359			359								359
Dividends declared on preferred stock	$ (4,344)	$ (4,344)	$ (4,344)	$ (688)	$ (688)	(688)
Dividends declared on common stock								(7,205)				(7,205)							(7,205)
Net income (loss)								12,114				12,114							12,114
Balance at Mar. 31, 2019			$ 124,262			$ 37,298		552,801	$ 205		389,431	1,605							552,801
Balance (in shares) at Mar. 31, 2019			127,125			1,571,734			20,567,694
Balance at Dec. 31, 2018			$ 122,137			$ 37,401		547,864	$ 204		386,394	1,728							547,864
Balance (in shares) at Dec. 31, 2018			125,000			1,571,734			20,430,218
Issuance of Operating Company ("OC") Units															$ 0
Stock dividend paid on preferred stock																			6,375
Other comprehensive income (loss) - derivative instruments																			(500)
Net income (loss)																			37,941
Balance at Sep. 30, 2019			$ 128,512			$ 37,298		589,417	$ 222		422,240	1,645	$ (500)						589,417
Balance (in shares) at Sep. 30, 2019			131,375			1,571,734			22,236,871
Balance at Mar. 31, 2019			$ 124,262			$ 37,298		552,801	$ 205		389,431	1,605							552,801
Balance (in shares) at Mar. 31, 2019			127,125			1,571,734			20,567,694
At-the-market issuance of common stock, net of offering costs								29,991	$ 15		29,976								29,991
At-the-market issuance of common stock, net of offering costs (in shares)									1,452,076
Stock dividend paid on preferred stock			$ 2,125					2,125											2,125
Stock dividend paid on preferred stock (in shares)			2,125
Repurchase and retirement of shares of common stock								(396)			(396)								(396)
Repurchase and retirement of shares of common stock (in shares)									(18,544)
Issuances of stock-based awards									$ 1		(1)
Issuances of stock-based awards (in shares)									133,730
Stock-based compensation								750			750								750
Forfeiture and retirement of shares related to stock-based awards (in shares)									(1,666)
Dividends declared on preferred stock	(4,407)	(4,407)	$ (4,407)	(688)	(688)	$ (688)
Dividends declared on common stock								(7,754)				(7,754)							(7,754)
Other comprehensive income (loss) - derivative instruments								(441)					(441)						(441)
Net income (loss)								14,874				14,874							14,874
Balance at Jun. 30, 2019			$ 126,387			$ 37,298		586,855	$ 221		419,760	3,630	(441)						586,855
Balance (in shares) at Jun. 30, 2019			129,250			1,571,734			22,133,290
At-the-market issuance of common stock, net of offering costs								1,901	$ 1		1,900								1,901
At-the-market issuance of common stock, net of offering costs (in shares)									96,081
Stock dividend paid on preferred stock			$ 2,125					2,125											2,125
Stock dividend paid on preferred stock (in shares)			2,125
Issuances of stock-based awards (in shares)									7,500
Stock-based compensation								580			580								580
Dividends declared on preferred stock	(4,469)	(4,469)	$ (4,469)	(688)	(688)	$ (688)
Dividends declared on common stock								(7,782)				(7,782)							(7,782)
Other comprehensive income (loss) - derivative instruments								(59)					(59)						(59)
Net income (loss)								10,954				10,954							10,954
Balance at Sep. 30, 2019			$ 128,512			$ 37,298		589,417	$ 222		422,240	1,645	(500)						589,417
Balance (in shares) at Sep. 30, 2019			131,375			1,571,734			22,236,871
Balance at Dec. 31, 2019			$ 130,637			$ 37,298		588,874	$ 224		426,129	(5,021)	(393)						588,874
Balance (in shares) at Dec. 31, 2019			133,500			1,571,734			22,423,283
At-the-market issuance of common stock, net of offering costs								15,072	$ 8		15,064								15,072
At-the-market issuance of common stock, net of offering costs (in shares)									810,000
Issuance of Operating Company ("OC") Units							$ 8,554			$ 8,554				$ 1,536	33,538		$ 1,536	$ 42,092
Stock dividend paid on preferred stock			$ 2,125					2,125											2,125
Stock dividend paid on preferred stock (in shares)			2,125
Repurchase and retirement of shares of common stock								(36)			(36)								(36)
Repurchase and retirement of shares of common stock (in shares)									(1,926)
Issuances of stock-based awards (in shares)									40,502
Stock-based compensation								607			607								607
Dividends declared on preferred stock	(4,519)	(4,519)	$ (4,519)	(688)	(688)	$ (688)
Dividends declared on common stock								(5,354)				(5,354)							(5,354)
Distributions declared to Non-controlling interests																$ (192)			(192)
Other comprehensive income (loss) - derivative instruments								(609)					(609)			(22)			(631)
Net income (loss)								(52,835)				(52,835)				(1,947)			(54,782)
Balance at Mar. 31, 2020			$ 132,762			$ 37,298		551,191	$ 232		450,318	(68,417)	(1,002)			32,913			584,104
Balance (in shares) at Mar. 31, 2020			135,625			1,571,734			23,271,859
Balance at Dec. 31, 2019			$ 130,637			$ 37,298		588,874	$ 224		426,129	(5,021)	(393)						588,874
Balance (in shares) at Dec. 31, 2019			133,500			1,571,734			22,423,283
Issuance of Operating Company ("OC") Units															$ 33,538
Stock dividend paid on preferred stock																			6,375
Other comprehensive income (loss) - derivative instruments																			(715)
Net income (loss)																			(61,407)
Balance at Sep. 30, 2020			$ 137,012			$ 37,298		535,351	$ 232		451,182	(89,289)	(1,084)			37,263			572,614
Balance (in shares) at Sep. 30, 2020			139,875			1,571,734			23,263,130
Balance at Mar. 31, 2020			$ 132,762			$ 37,298		551,191	$ 232		450,318	(68,417)	(1,002)			32,913			584,104
Balance (in shares) at Mar. 31, 2020			135,625			1,571,734			23,271,859
Issuance of Operating Company ("OC") Units														5,157			5,157
Stock dividend paid on preferred stock			$ 2,125					2,125											2,125
Stock dividend paid on preferred stock (in shares)			2,125
Equity offering costs related to issuance of common stock								(24)			(24)								(24)
Repurchase and retirement of shares of common stock								(363)			(363)								(363)
Repurchase and retirement of shares of common stock (in shares)									(27,629)
Issuances of stock-based awards (in shares)									18,900
Stock-based compensation								814			814								814
Dividends declared on preferred stock	(4,557)	(4,557)	$ (4,557)	(688)	(688)	$ (688)
Dividends declared on common stock								(5,351)				(5,351)							(5,351)
Distributions declared to Non-controlling interests																(433)			(433)
Other comprehensive income (loss) - derivative instruments								(266)					(266)			(21)			(287)
Net income (loss)								(341)				(341)				(652)			(993)
Balance at Jun. 30, 2020			$ 134,887			$ 37,298		542,540	$ 232		450,745	(79,354)	(1,268)			36,964			579,504
Balance (in shares) at Jun. 30, 2020			137,750			1,571,734			23,263,130
Issuance of Operating Company ("OC") Units														$ 1,285			$ 1,285
Stock dividend paid on preferred stock			$ 2,125					2,125											2,125
Stock dividend paid on preferred stock (in shares)			2,125
Stock-based compensation								437			437								437
Dividends declared on preferred stock	$ (4,621)	$ (4,621)	$ (4,621)	$ (688)	$ (688)	$ (688)
Other comprehensive income (loss) - derivative instruments								184					184			19			203
Net income (loss)								(4,626)				(4,626)				(1,005)			(5,631)
Balance at Sep. 30, 2020			$ 137,012			$ 37,298		$ 535,351	$ 232		$ 451,182	$ (89,289)	$ (1,084)			$ 37,263			$ 572,614
Balance (in shares) at Sep. 30, 2020			139,875			1,571,734			23,263,130

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net income (loss)	$ (61,407)	$ 37,941
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Interest capitalized on outstanding loans	(15,219)	(22,069)
Net unrealized (gain) loss on investments	5,630	(28,847)
Stock-based compensation	1,857	1,689
Equity in (earnings) losses from unconsolidated self-storage real estate venture	2,202	(399)
Return on investment from unconsolidated self-storage real estate venture	198	328
Depreciation and amortization	13,365	3,537
Amortization of deferred financing costs	2,055	1,440
Internalization - settlement of preexisting contractual relationship	37,353	0
Goodwill impairment loss	4,738	0
Accretion of origination fees	(834)	(867)
Unrealized gain on mark-to-market interest rate cap	208	89
Other	56	0
Changes in operating assets and liabilities:
Prepaid expenses and other assets	(1,460)	(1,346)
Due to Manager	(3,165)	(585)
Accounts payable, accrued expenses, and other liabilities	6,265	280
Net cash used in operating activities	(8,158)	(8,809)
Cash flows from investing activities:
Purchase of corporate fixed assets	(26)	(29)
Purchase of self-storage real estate owned	(29,970)	(10,347)
Capital additions to self-storage real estate owned	(354)	(1,309)
Capital contributions to unconsolidated self-storage real estate venture	(170)	(683)
Return of capital from unconsolidated self-storage real estate venture	4,683	3,833
Advances to unconsolidated self-storage real estate venture	(51)	(12,723)
Repayment of advances to unconsolidated self-storage real estate venture	355	12,773
Origination fees received in cash	0	1,114
Development property and bridge investments	(26,249)	(129,377)
Funding of other loans	0	(185)
Repayments of investment portfolio investments	13,878	361
Repayments of other loans	4,225	205
Net cash used in investing activities	(33,679)	(136,367)
Cash flows from financing activities:
Cash received from Credit Facility, net of issuance costs	74,671	124,261
Cash received from term loans, net of issuance costs	0	15,995
Stock repurchase	(399)	(468)
Net proceeds from issuance of common stock	15,004	34,645
Dividends paid on Non-controlling interest	(624)	0
Dividends paid on common stock	(18,638)	(22,108)
Net cash provided by financing activities	60,742	143,422
Net change in cash and cash equivalents	18,905	(1,754)
Cash and cash equivalents at the beginning of the period	3,278	8,715
Cash and cash equivalents at the end of the period	22,183	6,961
Series A Preferred Stock [Member]
Cash flows from financing activities:
Dividends paid on preferred stock	(7,208)	(6,736)
Series B Preferred Stock [Member]
Cash flows from financing activities:
Net proceeds (offering costs) from issuance of preferred stock	0	(103)
Dividends paid on preferred stock	$ (2,064)	$ (2,064)

ORGANIZATION AND FORMATION OF T

ORGANIZATION AND FORMATION OF THE COMPANY	9 Months Ended
	Sep. 30, 2020
ORGANIZATION AND FORMATION OF THE COMPANY [Abstract]
ORGANIZATION AND FORMATION OF THE COMPANY	1. ORGANIZATION AND FORMATION OF THE COMPANY Jernigan Capital, Inc. (together with its consolidated subsidiaries, the “Company”) makes debt and equity investments in self-storage development projects and existing self-storage facilities, most of which were recently constructed, and also owns self-storage facilities. The Company is a Maryland corporation that was organized on October 1, 2014 and completed its initial public offering (the “IPO”) on April 1, 2015. The Company is structured as an Umbrella Partnership REIT (“UPREIT”) and conducts its investment activities through its operating company, Jernigan Capital Operating Company, LLC (the “Operating Company”). Until February 20, 2020, the Company was externally managed by JCAP Advisors, LLC (the “Manager”). ​ On December 16, 2019, the Company, the Operating Company, the Manager, Dean Jernigan, John A. Good and Jonathan Perry entered into an Asset Purchase Agreement (the “Purchase Agreement”) providing for the acquisition by the Operating Company of substantially all of the operating assets and liabilities of the Manager (the “Internalization”). A special committee of the Board consisting solely of all of the independent and disinterested directors (the “Special Committee”) negotiated the terms of the Internalization on behalf of the Company and the Operating Company. The Purchase Agreement and the Internalization were unanimously approved by the Special Committee, and, upon recommendation by the Special Committee, by the Company’s Board of Directors. On February 20, 2020, the Company held a special meeting of common stockholders, at which the Company’s common stockholders approved the proposal necessary for the completion of the Internalization. On February 20, 2020, the Company completed the Internalization pursuant to the Purchase Agreement, and the Operating Company issued to the Manager 1,794,872 common units of limited liability company interest in the Operating Company (“OC Units”). In addition, if either (a) the Company’s common stock trades at or above a daily volume weighted average price of $25.00 per share for at least 30 days during any 365-day period prior to December 31, 2024 or (b) there is a change of control of the Company (as defined in the Purchase Agreement) prior to December 31, 2024 that is approved by the Company’s Board of Directors and the common stockholders of the Company, the Operating Company will issue an additional 769,231 OC Units to the Manager. The OC Units issued in the Internalization were Class B OC Units, so the initial distributions payable on the OC Units issued in the Internalization were prorated for the number of days during the initial distribution period that such OC Units were outstanding. The Class B OC Units were otherwise identical to Class A OC Units and automatically converted to Class A OC Units following the initial distribution period that ended April 15, 2020. Upon completion of the Internalization, the Company’s current employees, who were previously employed by the Manager, became employees of the Company and the functions previously performed by the Manager were internalized by the Company. As an internally managed company, the Company will no longer pay the Manager any fees or expense reimbursements arising from the Management Agreement (as defined in Note 11). Merger Agreement ​ On November 6, 2020, the Company consummated the transactions contemplated by that certain Agreement and Plan of Merger (the “Merger Agreement”), dated as of August 3, 2020, and amended September 21, 2020, by and among the Company, the Operating Company, NexPoint RE Merger, Inc. (“Parent”) and NexPoint RE Merger OP, LLC (the “Parent OP”). Pursuant to the terms and conditions set forth in the Merger Agreement, on November 6, 2020, the Parent merged with and into the Company, with the Company continuing as the surviving entity (the “Company Merger”) and immediately following the Company Merger, the Parent OP merged with and into the Operating Company, with the Operating Company continuing as the surviving entity (the “Operating Company Merger” and, together with the Company Merger, the “Mergers”). ​ At the effective time of the Company Merger (the “Company Merger Effective Time”), each share of Company common stock, $0.01 par value per share (the “Common Stock”) held by the Parent, Parent OP, or any subsidiary of the Company (a “Company Subsidiary”), was no longer outstanding and was automatically retired and ceased to exist, and no payment was made with respect thereto. Each share of Common Stock held by the Company in the Company’s treasury was automatically retired and ceased to exist, and no payment was made with respect thereto. All other shares of Common Stock issued and outstanding immediately prior to the Company Merger Effective Time were automatically converted into the right to receive an amount in cash equal to $17.30 per share, without interest (the “Merger Consideration”), and less any required withholding taxes. ​ At the Company Merger Effective Time, each share of the Company’s Series A Preferred Stock (the “Series A Preferred Shares”) issued and outstanding immediately prior to the Company Merger Effective Time was converted into the right to receive one validly issued, fully paid and non-assessable share of common stock, $0.01 par value of the surviving company (the “Series A Preferred Merger Consideration”), without interest, subject to any applicable withholding tax. All Series A Preferred Shares, so converted, are no longer outstanding and have automatically been cancelled and retired and have ceased to exist. ​ At the Company Merger Effective Time, each share of the Company’s 7.00% Series B Cumulative Redeemable Perpetual Preferred Stock (the “Series B Preferred Shares”) issued and outstanding immediately prior to the Company Merger Effective Time was converted into the right to receive the Series B liquidation value, pursuant to the terms of the Company’s charter (the “Series B Preferred Merger Consideration”), without interest, subject to any applicable withholding tax. All Series B Preferred Shares so converted, are no longer outstanding and have automatically been cancelled and retired and have ceased to exist. ​ At the effective time of the Operating Company Merger (“Operating Company Merger Effective Time”), (a) each Operating Company Unit (the “Operating Company Units”) issued and outstanding immediately prior to the Operating Company Merger Effective Time held by the Company was automatically converted into membership interests of the surviving operating company, (b) each Operating Company Unit (the “Operating Company Units”) issued and outstanding immediately prior to the Operating Company Merger Effective Time that was held by any Company Subsidiary is no longer outstanding and has automatically been retired and ceased to exist, and no payment has been made with respect thereto, and (c) each other Operating Company Unit issued and outstanding immediately prior to the Operating Company Merger Effective Time has automatically been converted into the right to receive an amount in cash equal to the Merger Consideration (the “Operating Company Merger Consideration”), and all Operating Company Units, so converted, are no longer outstanding and have automatically been cancelled, retired and have ceased to exist. ​ The Company has elected to be taxed as a real estate investment trust (“REIT”) under the Internal Revenue Code of 1986, as amended (the “Code”). As a REIT, the Company generally will not be subject to U.S. federal income taxes on REIT taxable income, determined without regard to the deduction for dividends paid and excluded capital gains, to the extent that it annually distributes all of its REIT taxable income to stockholders and complies with various other requirements for qualification as a REIT set forth in the Code.

SIGNIFICANT ACCOUNTING POLICIES

SIGNIFICANT ACCOUNTING POLICIES	9 Months Ended
	Sep. 30, 2020
SIGNIFICANT ACCOUNTING POLICIES [Abstract]
SIGNIFICANT ACCOUNTING POLICIES	Basis of Presentation ​ The Company’s consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying interim consolidated financial statements include all normal recurring adjustments that are, in the opinion of management, necessary for a fair presentation of the results for the interim periods included therein. Substantially all operations are conducted through the Operating Company, and all significant intercompany transactions and balances have been eliminated in consolidation. ​ Use of Estimates ​ The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect certain reported amounts and disclosures. Actual results could differ from those estimates. ​ Variable Interest Entities ​ The Company invests in entities that may qualify as variable interest entities (“VIEs”). A VIE is a legal entity that lacks one or more of the characteristics of a voting interest entity. A VIE is defined as an entity in which equity investors do not have the characteristics of a controlling financial interest or do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties. The determination of whether an entity is a VIE includes both a qualitative and quantitative analysis. Management bases the qualitative analysis on its review of the design of the entity, its organizational structure including allocation of decision-making authority and relevant financial agreements and the quantitative analysis on the forecasted cash flow of the entity. Management reassesses the initial evaluation of an entity as a VIE upon the occurrence of certain reconsideration events. ​ A VIE must be consolidated only by its primary beneficiary, which is defined as the party that, along with its affiliates and agents, has both the: (i) power to direct the activities that most significantly impact the VIE’s economic performance and (ii) obligation to absorb the losses of the VIE or the right to receive the benefits from the VIE, which could be significant to the VIE. Management determines whether the Company is the primary beneficiary of a VIE by considering qualitative and quantitative factors, including, but not limited to: which activities most significantly impact the VIE’s economic performance and which party controls such activities; the amount and characteristics of its investment; the obligation or likelihood for the Company or other interests to provide financial support; and consideration of the VIE’s purpose and design, including the risks the VIE was designed to create and pass through to its variable interest holders and the similarity with and significance to the Company’s business activities and the other interests. Management reassesses the determination of whether the Company is the primary beneficiary of a VIE each reporting period. ​ Equity Investments ​ Investments in real estate ventures and entities over which the Company exercises significant influence but not control are accounted for using the equity method. In accordance with Accounting Standards Codification (“ASC”) 825, Financial Instruments ​ Investments and Election of Fair Value Option of Accounting for Certain Investments ​ The Company has elected the fair value option of accounting for all of its development property investments that are required under GAAP to be accounted for under the equity method, in order to provide stockholders and others who rely on the Company’s financial statements with a more complete and accurate understanding of the Company’s economic performance including its revenues and value inherent in the Company’s equity participation in development projects. Changes in the fair value of these investments are recorded in net unrealized gain (loss) on investments within other income. Interest income is reported in interest income from investments in the Consolidated Statements of Operations and is not included in the net unrealized gain on investments within other income. All direct loan costs are charged to expense as incurred. ​ Each loan investment, including those recorded at cost and presented on the Consolidated Balance Sheets as other loans, is evaluated for impairment on a periodic basis. For loans carried at fair value, indicators of impairment are reflected in the measurement of the loan. For loans that are carried at cost, the Company estimates an allowance for loan loss at each reporting date. In evaluating loan impairment, the Company also periodically evaluates the extent and impact of any credit deterioration associated with the performance and/or value of the underlying collateral property as well as the financial and operating capability of the borrower on a loan by loan basis. The Company also evaluates the financial wherewithal of any loan guarantors as well as the borrower’s competency in managing and operating the property, including the impact of the COVID-19 pandemic on property operations. In addition, the Company considers the overall economic environment, real estate sector and geographic sub-market in which the borrower operates. A loan will be considered impaired when, based on current information and events, it is probable that the loan will not be collected according to the contractual terms of the loan agreement. Factors to be considered by management in determining impairment include payment status, collateral value and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. ​ Realized Gains and Net Unrealized Gain (Loss) on Investments ​ The Company measures realized gains by the difference between the net proceeds resulting from the sale of a self-storage property underlying one of the Company’s loan investments, excluding any prepayment penalties paid to the Company in connection with the repayment of the loan secured by the self-storage property, which are recognized in interest income from investments, and the cost basis of the investment, without regard to unrealized gain or loss previously recognized. “Net unrealized gain (loss) on investments” reflects the unrealized gains and losses recognized on certain investments during the reporting period, including any reversal of previously recorded unrealized gains when gains are realized. All fluctuations in fair value are included in net unrealized gain (loss) on investments on the Consolidated Statements of Operations. ​ Fair Value Measurement ​ The Company carries certain financial instruments at fair value because it has elected to apply the fair value option on an instrument by instrument basis under ASC 825-10. The Company’s financial instruments consist of cash, development property investments (which are generally structured as first mortgages and a 49.9% Profits Interest in the project), the investment in self-storage real estate venture, other loans, receivables, the secured revolving Credit Facility (as defined below), the term loans, payables, and derivative financial instruments. The following table presents the financial instruments measured at fair value on a recurring basis at September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Derivative financial instruments (asset position) ​ $ 47 ​ $ — ​ ​ 47 ​ ​ — Derivative financial instruments (liability position) ​ ​ (1,109) ​ ​ — ​ ​ (1,109) ​ ​ — Development property investments ​ ​ 316,254 ​ ​ — ​ ​ — ​ ​ 316,254 ​ The following table presents the financial instruments measured at fair value on a recurring basis at December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Derivative financial instruments (asset position) ​ $ 14 ​ $ — ​ $ 14 ​ $ — Derivative financial instruments (liability position) ​ ​ (393) ​ ​ — ​ ​ (393) ​ ​ — Development property investments ​ ​ 549,684 ​ ​ — ​ ​ — ​ ​ 549,684 ​ Estimating fair value requires the use of judgment. The types of judgments involved depend upon the availability of observable market information. Management’s judgments include determining the appropriate valuation model to use, estimating unobservable inputs and applying valuation adjustments. See Note 4, Fair Value of Financial Instruments ​ Derivative Instruments and Hedging Activities ​ All derivative financial instruments are recorded on the balance sheet at fair value. Changes in fair value are recognized either in earnings or as other comprehensive income (loss), depending on whether the derivative has been designated as a fair value or cash flow hedge and whether it qualifies as part of a hedging relationship, the nature of the exposure being hedged, and how effective the derivative is at offsetting movements in underlying exposure. Hedge accounting is discontinued when it is determined that the derivative is no longer effective in offsetting changes in the fair value or cash flows of a hedged item; the derivative expires or is sold, terminated, or exercised; it is no longer probable that the forecasted transaction will occur; or management determines that designating the derivative as a hedging instrument is no longer appropriate. The Company uses interest rate swaps and interest rate caps to effectively convert a portion of its variable rate debt to fixed rate, thus reducing the impact of changes in interest rates on interest payments (see Note 7, Debt, Risk Management and Use of Financial Instruments ​ The changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in “Accumulated other comprehensive income (loss)” and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. In accordance with ASU 2017-12, Derivatives and Hedging (Topic 815) as long as a hedging instrument is designated and the results of the effectiveness testing support that the instrument qualifies for hedge accounting treatment, there is no longer the requirement for periodic measurement or recognition of ineffectiveness. Rather, the full impact of hedge gains and losses will be recognized in the period in which hedged transactions impact earnings, regardless of whether or not economic mismatches exist in the hedging relationship. Amounts reported in “Accumulated other comprehensive income (loss)” related to derivatives designated as qualifying cash flow hedges will be reclassified to interest expense as interest payments are made on the Company's variable rate or fixed rate debt. Changes in fair value for financial instruments not designated as cash flow hedges are recognized in earnings within interest expense in the Consolidated Statements of Operations. ​ Self-Storage Real Estate Owned ​ To date, all self-storage real estate owned has consisted of self-storage facilities that were developed and constructed with financing provided by the Company. Each facility collateralized a mortgage loan that, together with the related Profits Interest, was reported by the Company as a development property investment carried at fair value. Each such property became self-storage real estate owned during the period when the Company acquired the developer’s interest in the entity that owns the facility. After such time, fair value accounting for such investment ceases. ​ Land is carried at historical cost. Building and improvements are carried at historical cost less accumulated depreciation and impairment losses. The cost consists primarily of: (i) the funded principal balance of the loan to the Company, net of unamortized origination fees; (ii) unrealized appreciation recognized as of the acquisition date; and (iii) the cash consideration paid and assumed liabilities, if applicable, to acquire the interests of other equity owners of the project. Ordinary repairs and maintenance are expensed as incurred; major replacements and betterments, which improve or extend the life of the asset, are capitalized and depreciated over their estimated useful lives. The costs of building and improvements are generally depreciated using the straight-line method based on a useful life of 40 years. ​ All of the Company’s acquisitions have been asset acquisitions and the Company expects that the majority of future self-storage facility acquisitions will be considered asset acquisitions, however, the Company will continue to evaluate each future acquisition using Accounting Standards Update (“ASU”) 2017-01 - Business Combinations (Topic 805): Clarifying the Definition of a Business to determine whether accounting for a business combination or asset acquisition applies. When facilities are acquired, the cost is allocated to the tangible and intangible assets acquired and liabilities assumed based on relative fair values. Allocations to the individual assets and liabilities are based upon their relative fair values as estimated by management. ​ In allocating the purchase price for an acquisition, the Company determines whether the acquisition includes intangible assets or liabilities. The Company allocates a portion of the cost to an intangible asset attributable to the value of in-place leases. This intangible asset is amortized to expense over the expected remaining term of the respective leases, which is generally one year. Substantially all the leases in place at acquired facilities are at market rates, as the majority of the leases are month-to-month contracts. Accordingly, to date, no portion of the basis for an acquired property has been allocated to above- or below-market lease intangibles. To date, no intangible asset has been recorded for the value of customer relationships, because the Company does not have any concentrations of significant customers and the average customer turnover is frequent. ​ The Company evaluates long-lived assets for impairment when events and circumstances, such as declines in occupancy and operating results, indicate that there may be an impairment. The carrying value of these long-lived assets is compared to the undiscounted future net operating cash flows, plus a terminal value, attributable to the assets to determine if the facility’s basis is recoverable. If an asset’s basis is not considered recoverable, an impairment loss is recorded to the extent the net carrying value of the asset exceeds the fair value. The impairment loss recognized equals the excess of net carrying value over the related fair value of the asset. There were no impairment losses recognized in accordance with these procedures during the three or nine months ended September 30, 2020 or during the year ended December 31, 2019. ​ Cash and Cash Equivalents ​ Cash, investments in money market accounts and certificates of deposit with original maturities of three months or less are considered to be cash equivalents. The Company places its cash and cash equivalents primarily with three financial institutions, and the balance at two of the financial institutions exceeds the Federal Deposit Insurance Corporation insurance limit. ​ Other Loans ​ The Company’s other loans balance primarily includes principal balances for certain revolving loan agreements, short-term mortgage loans, and land loans made by the Company in situations where it was determined that making such loans would benefit the Company’s primary business. These loans are accounted for under the cost method, and fair value approximates cost at September 30, 2020 and December 31, 2019. None of these loans are in non-accrual status as of September 30, 2020 and December 31, 2019. The Company determined that no allowance for loan loss was necessary at September 30, 2020 and December 31, 2019. ​ Fixed Assets ​ Fixed assets are recorded at cost and consist of furniture, office and computer equipment, and software. Depreciation is computed on a straight-line basis over the estimated useful lives of the related assets, which range from three ​ Goodwill ​ Goodwill represents the excess of consideration paid over the fair value of underlying identifiable net assets of businesses acquired. During the nine months ended September 30, 2020, the Company recorded $4.7 million of Goodwill related to the Internalization, and the Company has one reporting unit. Goodwill has an indeterminate life and is not amortized, but is tested for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the asset might be impaired. Subsequent to the Internalization, the Company determined that dramatically deteriorating macroeconomic conditions driven by the impact of the COVID-19 pandemic on capital markets, and specifically the Company’s market capitalization, was a triggering event for an interim goodwill impairment test. In accordance with ASC 350, Intangibles - Goodwill and Other , since the Company’s common stock is traded in an active market, the Company calculated its fair value primarily based on the Company’s market capitalization as of March 31, 2020. The fair value calculated as of March 31, 2020, was determined to be below the Company’s carrying value. As a result, the Company recorded a goodwill impairment loss of $4.7 million for the nine months ended September 30, 2020, and there is no Goodwill as of September 30, 2020 or December 31, 2019. ​ Revenue Recognition ​ Interest income is recognized as earned on a simple interest basis and is reported in interest income from investments in the Consolidated Statements of Operations. Accrual of interest will be discontinued on a loan when management believes, after considering economic and business conditions and collection efforts, that the borrower’s financial condition is such that collection of interest is doubtful. The Company will recognize income on impaired loans when they are placed into non-accrual status on a cash basis when the loans are both current and the collateral on the loan is sufficient to cover the outstanding obligation to the Company. If these factors do not exist, the Company will not recognize income on such loans. ​ The Company’s loan origination fees are accreted into interest income over the term of the investment using the effective yield method. ​ The operations of the self-storage real estate owned are managed by a third-party self-storage management company. All rental leases are operating leases, and rental income is recognized in accordance with the terms of the leases, which generally are month to month. Debt Issuance Costs ​ Costs related to the issuance of a debt instrument are deferred and amortized as interest expense over the estimated life of the related debt instrument using the straight-line method, which approximates the effective interest method. If a debt instrument is repurchased, modified, or exchanged prior to its original maturity date, the Company evaluates both the unamortized balance of debt issuance costs as well as any new debt issuance costs, including third party fees, to determine if the costs should be written off to interest expense or, if significant, included in “loss on modification or extinguishment of debt” in the Consolidated Statements of Operations. Debt issuance costs related to the term loans are presented in the Consolidated Balance Sheets as a deduction from the carrying amount of the principal balance. Debt issuance costs related to the revolving Credit Facility are presented in the Consolidated Balance Sheets as Deferred Financing Costs. ​ Internalization Expenses As described in Note 1, Organization and Formation ​ ​ ​ ​ ​ OC Units issuable as Initial Consideration (1) : $ 33,538 ​ OC Units contingently issuable as Earn Out Consideration (2) : ​ 8,554 ​ ​ $ 42,092 ​ (1) Represents the fair value of 1,794,872 OC Units issuable as the Initial Consideration based upon the Company's closing stock price as of February 20, 2020 of $20.31 adjusted for an 8% marketability discount for the fair value impact of the one year holding period and annual limits on selling of OC Units. (2) Represents the fair value of 769,231 OC Units issuable as the Earn Out Consideration contingent upon (1) the Company’s common stock trading at or above a daily volume weighted price of $25.00 per share for at least 30 days during any trailing 365-day period prior to December 31, 2024, or (2) a change of control of the Company that is approved by the board of directors and stockholders of the Company occurring prior to December 31, 2024, based on a Black-Scholes Merton valuation of the OC Units. The significant assumptions utilized in the valuation of the Earn Out Consideration were a risk-free rate of 1.41% , a dividend yield of 4.53% , volatility of 27% , and a marketability discount of 8% . ​ In accordance with ASC 805, Business Combinations excess consideration paid over the fair value of underlying identifiable net assets of businesses acquired was recorded as Goodwill. The table below presents the revenue and net income of the business combination on a pro forma basis as if the Internalization occurred on January 1, 2019. As the Manager’s historical revenues were entirely comprised of amounts received from the Company for management services performed by the Manager and intercompany amounts are eliminated in consolidation, there was no pro forma adjustment to the Company’s revenue for the nine months ended September 30, 2020 and 2019. Pro forma net loss for the nine months ended September 30, 2020 includes the elimination of non-recurring expenses for the settlement of the pre-existing contractual agreement of $37.4 million and acquisition related expenses of $0.4 million. Pro forma adjustments for the periods ended September 30, 2020 and 2019, also include the impact of additional compensation expense for employees previously employed by the Manager and the elimination of fees paid to the Manager. The pro forma results are not necessarily indicative of the results which actually would have occurred if the business combination had occurred on the first day of the periods presented, nor does the pro forma financial information purport to represent the results of operations for future periods. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ Nine Months Ended September 30, 2019 Pro forma total revenue (unaudited) $ 35,242 ​ ​ ​ $ 32,965 ​ Pro forma net income (loss) allocable to common shares (unaudited) ​ (35,236) ​ ​ ​ ​ 25,882 ​ ​ Offering and Registration Costs ​ Offering and registration costs represent underwriting discounts and commissions, professional fees, fees paid to various regulatory agencies, and other costs incurred in connection with the registration and sale of the Company’s securities. Offering and registration costs incurred in connection with the Company’s stock offerings are reflected as a reduction of additional paid-in capital. ​ Income Taxes ​ The Company has elected to be taxed as a REIT and to comply with the related provisions of the Code. Accordingly, the Company will generally not be subject to U.S. federal income tax to the extent of its distributions to stockholders and as long as certain asset, income and share ownership tests are met. To qualify as a REIT, the Company must annually distribute at least 90% of its REIT taxable income to its stockholders and meet certain other requirements. ​ Earnings per Share (“EPS”) ​ Basic EPS includes only the weighted average number of common shares outstanding during the period. Diluted EPS includes the weighted average number of common shares and the dilutive effect of restricted stock, accrued stock dividends, and redeemable OC Units when such instruments are dilutive. ​ All outstanding unvested share-based payment awards that contain rights to nonforfeitable dividends are treated as participating in undistributed earnings with common shareholders. Awards of this nature are considered participating securities and the two-class method of computing basic and diluted EPS must be applied. Beginning on the first anniversary of the date of issuance, OC Units may be tendered for redemption by the holder thereof for cash per OC Unit equal to the then-current market price of the Company’s common stock, or at the Company’s option, shares of the Company’s common stock on a one-for-one basis and the income allocable to such OC Units is allocated on this same basis and reflected as non-controlling interests in the accompanying consolidated financial statements. The Company’s diluted earnings per share represents the more dilutive of the treasury stock or two-class methods and OC Units are included in dilutive earnings per share calculations when the units are dilutive to earnings per share. Net losses are not attributed to participating securities and net loss attributable to common shareholders is adjusted for dividends declared on unvested restricted shares in periods with a net loss. Diluted earnings per share includes contingently issuable OC Units only if the market condition would have been met had the end of the reporting period been the measurement period. Stock awards with a market condition do not participate in nonforfeitable rights to dividends and are excluded from the calculation of diluted EPS. ​ Segment Reporting ​ The Company does not evaluate performance on a relationship specific or transactional basis and does not distinguish its principal business or group its operations on a geographical basis for purposes of measuring performance. Accordingly, the Company believes it has a single ​ Recent Accounting Pronouncements ​ In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This ASU significantly changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. This guidance is effective for smaller reporting companies for fiscal years and for interim periods within those fiscal years, beginning after December 15, 2022, with early adoption being allowed as of the fiscal years beginning after December 15, 2018. The Company is currently assessing the impact this new accounting guidance will have on its consolidated financial statements; however, the Company does not expect the new accounting guidance to have a material impact on its consolidated financial statements. ​ In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848). This ASU contains practical expedients for reference rate reform related activities that impact debt, leases, derivatives and other contracts. The guidance in this ASU is optional and may be elected over time as reference rate reform activities occur. For the three and nine months ended September 30, 2020, the Company has elected to apply the hedge accounting expedients related to probability and the assessments of effectiveness for future LIBOR-indexed cash flows to assume that the index upon which future hedged transactions will be based matches the index on the corresponding derivatives. Application of these expedients preserves the presentation of derivatives consistent with past presentation. The Company continues to evaluate the impact of the guidance and may apply other elections as applicable as additional changes in the market occur. ​ Consolidated Statements of Cash Flows - Supplemental Disclosures ​ The following table provides supplemental disclosures related to the Consolidated Statements of Cash Flows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, ​ ​ 2020 ​ 2019 Supplemental disclosure of cash flow information: ​ ​ ​ ​ ​ ​ Interest paid ​ $ 6,986 ​ $ 3,359 ​ ​ ​ ​ ​ ​ ​ Supplemental disclosure of non-cash investing and financing activities: ​ ​ ​ ​ ​ ​ Stock dividend paid on preferred stock ​ $ 6,375 ​ $ 6,375 Dividends declared, but not paid, on preferred stock ​ ​ 5,309 ​ ​ 5,157 Dividends declared, but not paid, on common stock ​ ​ — ​ ​ 7,783 Dividends declared, but not paid, on OC Units ​ ​ — ​ ​ — Reclassification of development property investments to self-storage real estate owned ​ ​ 255,495 ​ ​ 125,715 Reclassification of other assets and liabilities to self-storage real estate owned ​ ​ 1,074 ​ ​ — Other loans paid off with issuance of development property investments ​ ​ — ​ ​ 404 OC Units issued for self-storage real estate owned acquisitions ​ ​ 7,978 ​ ​ — OC Units issued for Internalization ​ ​ 33,538 ​ ​ — Contingent consideration for Internalization ​ ​ 8,554 ​ ​ — ​

SELF-STORAGE INVESTMENT PORTFOL

SELF-STORAGE INVESTMENT PORTFOLIO	9 Months Ended
	Sep. 30, 2020
SELF-STORAGE INVESTMENT PORTFOLIO [Abstract]
SELF-STORAGE INVESTMENT PORTFOLIO	3. SELF-STORAGE INVESTMENT PORTFOLIO ​ The Company’s self-storage investments at September 30, 2020 consisted of the following: ​ Investments reported at fair value ​ ● Development Property Investments The Company has commenced foreclosure proceedings against the borrower of its $14.3 million Philadelphia development property investment because the borrower has defaulted under the loan by, among other things, failing to pay the general contractor. The total unpaid balance of the loan, before considering protective advances and unpaid interest, is $11.5 million. As the investment was a collateral dependent loan, the Company considered the fair value of the collateral when determining the fair value of the investment as of September 30, 2020. The Company has also commenced foreclosure proceedings against the borrower of its $14.8 million Houston development property because the borrower has defaulted under the loan by, among other things, failing to pay interest and operating expenses with respect to the property. The total unpaid balance of the loan, before considering protective advances and unpaid interest, is $14.8 million. As the investment was a collateral dependent loan, the Company considered the fair value of the collateral when determining the fair value of the investment as of September 30, 2020. ​ As of September 30, 2020, the aggregate committed principal amount of the Company’s development property investments was approximately $314.5 million and outstanding principal was $283.3 million, as described in more detail in the table below (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Metropolitan ​ Total ​ ​ ​ ​ Remaining ​ ​ ​ ​ ​ Statistical Area ​ Investment ​ Funded ​ Unfunded ​ ​ ​ Closing Date ​ ("MSA") ​ Commitment ​ Investment (1) ​ Commitment ​ Fair Value Development property investments (includes a profits interest): ​ ​ ​ ​ ​ ​ ​ ​ ​ 7/2/2015 ​ Milwaukee (2)(7) ​ $ 7,650 ​ $ 7,648 ​ $ 2 ​ $ 8,316 10/27/2015 ​ Austin (2)(7) ​ ​ 8,658 ​ ​ 8,184 ​ ​ 474 ​ ​ 8,071 2/24/2017 ​ New Orleans (2)(7) ​ ​ 12,549 ​ ​ 12,371 ​ ​ 178 ​ ​ 15,017 3/1/2017 ​ Houston (2)(9) ​ ​ 14,825 ​ ​ 14,825 ​ ​ — ​ ​ 15,661 5/2/2017 ​ Tampa 2 (2)(7) ​ ​ 8,091 ​ ​ 7,984 ​ ​ 107 ​ ​ 9,444 5/19/2017 ​ Tampa 3 (2)(7) ​ ​ 9,224 ​ ​ 8,618 ​ ​ 606 ​ ​ 10,561 6/12/2017 ​ Tampa 4 (2)(7) ​ ​ 10,266 ​ ​ 10,014 ​ ​ 252 ​ ​ 13,317 6/29/2017 ​ Boston 1 (2)(6) ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,850 8/30/2017 ​ Orlando 4 (2)(7) ​ ​ 9,037 ​ ​ 8,329 ​ ​ 708 ​ ​ 10,376 9/14/2017 ​ Los Angeles 1 ​ ​ 28,750 ​ ​ 10,923 ​ ​ 17,827 ​ ​ 11,143 9/14/2017 ​ Miami 1 (3) ​ ​ 14,657 ​ ​ 14,463 ​ ​ 194 ​ ​ 15,657 10/12/2017 ​ Miami 2 (4)(10) ​ ​ — ​ ​ 1,661 ​ ​ — ​ ​ 1,459 10/30/2017 ​ New York City 3 (4)(10) ​ ​ — ​ ​ 8,261 ​ ​ — ​ ​ 7,916 11/16/2017 ​ Miami 3 (2)(4)(7) ​ ​ 20,168 ​ ​ 19,093 ​ ​ 1,745 ​ ​ 21,914 12/15/2017 ​ New York City 4 (2)(7) ​ ​ 10,591 ​ ​ 9,747 ​ ​ 844 ​ ​ 11,435 12/28/2017 ​ New York City 5 (2) ​ ​ 16,073 ​ ​ 16,064 ​ ​ 9 ​ ​ 17,646 3/30/2018 ​ Philadelphia (2)(4)(8) ​ ​ 14,338 ​ ​ 11,536 ​ ​ 3,264 ​ ​ 11,313 5/1/2018 ​ Miami 9 (4)(10) ​ ​ — ​ ​ 3,877 ​ ​ — ​ ​ 3,639 5/15/2018 ​ Atlanta 7 (2)(7) ​ ​ 9,418 ​ ​ 8,502 ​ ​ 916 ​ ​ 9,948 5/23/2018 ​ Kansas City (2)(7) ​ ​ 9,968 ​ ​ 8,754 ​ ​ 1,214 ​ ​ 10,489 6/7/2018 ​ Orlando 5 (2) ​ ​ 12,969 ​ ​ 12,057 ​ ​ 912 ​ ​ 13,885 11/16/2018 ​ Baltimore 2 (10) ​ ​ — ​ ​ 785 ​ ​ — ​ ​ 690 3/1/2019 ​ New York City 6 ​ ​ 18,796 ​ ​ 4,297 ​ ​ 14,499 ​ ​ 4,311 4/18/2019 ​ New York City 7 (3)(4) ​ ​ 23,462 ​ ​ 15,781 ​ ​ 8,050 ​ ​ 17,374 ​ ​ ​ ​ $ 259,490 ​ $ 223,774 ​ $ 51,801 ​ $ 253,432 Preferred equity investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 6/12/2018 ​ Los Angeles 2 (3)(5) ​ ​ 9,298 ​ ​ 9,659 ​ ​ 649 ​ ​ 10,384 3/15/2019 ​ Stamford (2)(5) ​ ​ 2,904 ​ ​ 3,222 ​ ​ — ​ ​ 5,479 5/8/2019 ​ New York City 8 (5) ​ ​ 21,000 ​ ​ 23,073 ​ ​ — ​ ​ 23,492 7/11/2019 ​ New York City 9 (5) ​ ​ 13,095 ​ ​ 14,218 ​ ​ — ​ ​ 14,177 8/21/2019 ​ New York City 10 (5) ​ ​ 8,674 ​ ​ 9,346 ​ ​ — ​ ​ 9,290 ​ ​ ​ ​ $ 54,971 ​ $ 59,518 ​ $ 649 ​ $ 62,822 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investments reported at fair value ​ $ 314,461 ​ $ 283,292 ​ $ 52,450 ​ $ 316,254 ​ (1) (2) Fair Value of Financial Instruments (3) Fair Value of Financial Instruments (4) (5) (6) (7) (8) (9) (10) The Company has re-assessed these development property investments for which either development or construction has not yet commenced and communicated our intent to forgo those projects with the respective developers. The Company and its respective developer partners on these investments are in active dialogues concerning the repayment of its outstanding principal along with any current and future accrued interest. ​ The following table provides a reconciliation of the funded principal to the fair market value of investments at September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ Funded principal $ 283,292 Adjustments: ​ ​ ​ Unamortized origination and other fees ​ ​ (3,292) Net unrealized gain (loss) on investments ​ ​ 36,340 Other ​ ​ (86) Fair value of investments ​ $ 316,254 ​ As of December 31, 2019, the aggregate committed principal amount of the Company’s development property investments was approximately $608.9 million and outstanding principal was $478.6 million, as described in more detail in the table below (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Metropolitan ​ Total ​ ​ ​ ​ Remaining ​ ​ ​ ​ ​ Statistical Area ​ Investment ​ Funded ​ Unfunded ​ ​ ​ Closing Date ​ ("MSA") ​ Commitment ​ Investment (1) ​ Commitment ​ Fair Value Development property investments (includes a profits interest): ​ ​ ​ ​ ​ ​ ​ ​ ​ 7/2/2015 ​ Milwaukee (2)(7) ​ $ 7,650 ​ $ 7,648 ​ $ 2 ​ $ 8,884 8/14/2015 ​ Raleigh (2)(7)(10) ​ ​ 8,792 ​ ​ 8,789 ​ ​ 3 ​ ​ 8,593 10/27/2015 ​ Austin (2)(7) ​ ​ 8,658 ​ ​ 8,136 ​ ​ 522 ​ ​ 8,099 9/20/2016 ​ Charlotte 2 (2)(7)(10) ​ ​ 12,888 ​ ​ 12,677 ​ ​ 211 ​ ​ 13,984 1/18/2017 ​ Atlanta 3 (2)(7)(10) ​ ​ 14,115 ​ ​ 13,297 ​ ​ 818 ​ ​ 16,130 1/31/2017 ​ Atlanta 4 (2)(7)(10) ​ ​ 13,678 ​ ​ 13,497 ​ ​ 181 ​ ​ 17,082 2/24/2017 ​ Orlando 3 (2)(7)(10) ​ ​ 8,056 ​ ​ 7,767 ​ ​ 289 ​ ​ 9,725 2/24/2017 ​ New Orleans (2)(7) ​ ​ 12,549 ​ ​ 12,021 ​ ​ 528 ​ ​ 14,504 2/27/2017 ​ Atlanta 5 (2)(7)(10) ​ ​ 17,492 ​ ​ 17,492 ​ ​ — ​ ​ 19,970 3/1/2017 ​ Fort Lauderdale (2)(7)(10) ​ ​ 9,952 ​ ​ 9,383 ​ ​ 569 ​ ​ 13,635 3/1/2017 ​ Houston (2)(9) ​ ​ 14,825 ​ ​ 14,825 ​ ​ — ​ ​ 17,820 4/14/2017 ​ Louisville 1 (2)(7)(10) ​ ​ 8,523 ​ ​ 7,552 ​ ​ 971 ​ ​ 9,550 4/20/2017 ​ Denver 1 (2)(7)(10) ​ ​ 9,806 ​ ​ 9,616 ​ ​ 190 ​ ​ 10,947 4/20/2017 ​ Denver 2 (2)(7) ​ ​ 11,164 ​ ​ 11,009 ​ ​ 155 ​ ​ 12,383 5/2/2017 ​ Atlanta 6 (2)(7)(10) ​ ​ 12,543 ​ ​ 12,025 ​ ​ 518 ​ ​ 14,744 5/2/2017 ​ Tampa 2 (2)(7) ​ ​ 8,091 ​ ​ 7,644 ​ ​ 447 ​ ​ 9,196 5/19/2017 ​ Tampa 3 (2)(7) ​ ​ 9,224 ​ ​ 8,326 ​ ​ 898 ​ ​ 10,086 6/12/2017 ​ Tampa 4 (2)(7) ​ ​ 10,266 ​ ​ 9,614 ​ ​ 652 ​ ​ 12,673 6/19/2017 ​ Baltimore 1 (2)(4)(7)(10) ​ ​ 10,775 ​ ​ 11,010 ​ ​ 274 ​ ​ 13,581 6/28/2017 ​ Knoxville (2)(7)(10) ​ ​ 9,115 ​ ​ 8,628 ​ ​ 487 ​ ​ 10,355 6/29/2017 ​ Boston 1 (2)(6) ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,361 6/30/2017 ​ New York City 2 (2)(4)(10) ​ ​ 27,982 ​ ​ 28,974 ​ ​ 665 ​ ​ 31,047 7/27/2017 ​ Jacksonville 3 (2)(7)(10) ​ ​ 8,096 ​ ​ 7,751 ​ ​ 345 ​ ​ 10,129 8/30/2017 ​ Orlando 4 (2)(7) ​ ​ 9,037 ​ ​ 8,107 ​ ​ 930 ​ ​ 10,251 9/14/2017 ​ Los Angeles 1 ​ ​ 28,750 ​ ​ 10,157 ​ ​ 18,593 ​ ​ 10,347 9/14/2017 ​ Miami 1 (3) ​ ​ 14,657 ​ ​ 12,618 ​ ​ 2,039 ​ ​ 13,373 9/28/2017 ​ Louisville 2 (2)(7)(10) ​ ​ 9,940 ​ ​ 9,530 ​ ​ 410 ​ ​ 11,688 10/12/2017 ​ Miami 2 (4) ​ ​ 9,459 ​ ​ 1,494 ​ ​ 8,045 ​ ​ 1,280 10/30/2017 ​ New York City 3 (4) ​ ​ 15,301 ​ ​ 6,776 ​ ​ 8,822 ​ ​ 6,383 11/16/2017 ​ Miami 3 (3)(4) ​ ​ 20,168 ​ ​ 12,086 ​ ​ 8,413 ​ ​ 12,898 11/21/2017 ​ Minneapolis 1 (2)(7)(10) ​ ​ 12,674 ​ ​ 10,684 ​ ​ 1,990 ​ ​ 12,290 12/1/2017 ​ Boston 2 (2)(7)(10) ​ ​ 8,771 ​ ​ 7,918 ​ ​ 853 ​ ​ 10,024 12/15/2017 ​ New York City 4 (3) ​ ​ 10,591 ​ ​ 6,705 ​ ​ 3,886 ​ ​ 7,528 12/27/2017 ​ Boston 3 ​ ​ 10,174 ​ ​ 2,757 ​ ​ 7,417 ​ ​ 2,674 12/28/2017 ​ New York City 5 (2) ​ ​ 16,073 ​ ​ 13,817 ​ ​ 2,256 ​ ​ 16,373 2/8/2018 ​ Minneapolis 2 (2)(7)(10)) ​ ​ 10,543 ​ ​ 9,904 ​ ​ 639 ​ ​ 11,763 3/30/2018 ​ Philadelphia (2)(4)(8) ​ ​ 14,338 ​ ​ 11,536 ​ ​ 3,263 ​ ​ 11,807 4/6/2018 ​ Minneapolis 3 (2)(7)(10) ​ ​ 12,883 ​ ​ 10,337 ​ ​ 2,546 ​ ​ 12,043 5/1/2018 ​ Miami 9 (4) ​ ​ 12,421 ​ ​ 3,560 ​ ​ 9,006 ​ ​ 3,427 5/15/2018 ​ Atlanta 7 (3) ​ ​ 9,418 ​ ​ 6,563 ​ ​ 2,855 ​ ​ 7,683 5/23/2018 ​ Kansas City (2) ​ ​ 9,968 ​ ​ 8,235 ​ ​ 1,733 ​ ​ 9,663 6/7/2018 ​ Orlando 5 (2) ​ ​ 12,969 ​ ​ 10,340 ​ ​ 2,629 ​ ​ 11,780 11/16/2018 ​ Baltimore 2 ​ ​ 9,247 ​ ​ 757 ​ ​ 8,490 ​ ​ 709 3/1/2019 ​ New York City 6 ​ ​ 18,796 ​ ​ 3,168 ​ ​ 15,628 ​ ​ 3,122 4/18/2019 ​ New York City 7 (4) ​ ​ 23,462 ​ ​ 7,304 ​ ​ 16,287 ​ ​ 7,067 ​ ​ ​ ​ $ 553,880 ​ $ 422,034 ​ $ 135,455 ​ $ 490,651 Preferred equity investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 6/12/2018 ​ Los Angeles 2 (5) ​ ​ 9,298 ​ ​ 9,173 ​ ​ 649 ​ ​ 9,403 3/15/2019 ​ Stamford (2)(5) ​ ​ 2,904 ​ ​ 3,064 ​ ​ — ​ ​ 4,952 5/8/2019 ​ New York City 8 (5) ​ ​ 21,000 ​ ​ 21,945 ​ ​ — ​ ​ 22,359 7/11/2019 ​ New York City 9 (5) ​ ​ 13,095 ​ ​ 13,526 ​ ​ — ​ ​ 13,489 8/21/2019 ​ New York City 10 (5) ​ ​ 8,674 ​ ​ 8,892 ​ ​ — ​ ​ 8,830 ​ ​ ​ ​ $ 54,971 ​ $ 56,600 ​ $ 649 ​ $ 59,033 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investments reported at fair value ​ $ 608,851 ​ $ 478,634 ​ $ 136,104 ​ $ 549,684 (1) (2) Fair Value of Financial Instruments (3) Fair Value of Financial Instruments (4) (5) (6) (7) (8) (9) (10) During the nine months ended September 30, 2020, the Company purchased its partner’s 50.1% Profits Interest in this investment. ​ The following table provides a reconciliation of the funded principal to the fair market value of investments at December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ Funded principal $ 478,634 Adjustments: ​ ​ ​ Unamortized origination and other fees ​ ​ (5,633) Net unrealized gain (loss) on investments ​ ​ 76,767 Other ​ ​ (84) Fair value of investments ​ $ 549,684 ​ The Company has elected the fair value option of accounting for all of its investment portfolio investments in order to provide stockholders and others who rely on the Company’s financial statements with a more complete and accurate understanding of the Company’s economic performance, including its revenues and value inherent in its equity participation in development projects. See Note 4, Fair Value of Financial Instruments ​ No loans, with the exception of the $14.3 million Philadelphia and $14.8 Houston development property investments, were in non-accrual status as of September 30, 2020. No loans, with the exception of the $14.8 Houston development property investment, were in non-accrual status as of December 31, 2019. ​ All of the Company’s development property investments with a Profits Interest would have been accounted for under the equity method had the Company not elected the fair value option. For these investments with a Profits Interest, the assets and liabilities of the equity method investees approximated $377.9 million and $341.7 million, respectively, at September 30, 2020 and approximated $592.3 million and $531.7 million, respectively, at December 31, 2019. These investees had revenues of approximately $1.9 million and $4.7 million and operating expenses of approximately $1.1 million and $2.7 million for the three and nine months ended September 30, 2020, respectively. These investees had revenues of approximately $2.3 million and $4.5 million and operating expenses of approximately $2.7 million and $6.4 million for the three and nine months ended September 30, 2019, respectively. During the three and nine months ended September 30, 2020 and 2019, no individual investment comprised more than 20% of the Company’s net income (loss). ​ For three and sixteen of the Company’s development property investments with a Profits Interest as of September 30, 2020 and December 31, 2019, respectively, an investor has an option to put its interest to the Company upon the event of default of the underlying property loans. The put, if exercised, requires the Company to purchase the member’s interest at the original purchase price plus a yield of 4.5% on such purchase price. The Company concluded that the likelihood of loss is remote and assigned no value to these put provisions as of September 30, 2020 and December 31, 2019. ​ Investments reported at cost (Self-Storage Real Estate Owned) ​ 2020 Activity ​ On February 10, 2020, the Company purchased 100% of the Class A membership units of the limited liability company that owned the Charlotte II, Knoxville, Louisville 1, Atlanta 3, Atlanta 5 and Atlanta 6 development property investments with a Profits Interest. On February 14, 2020, the Company purchased 100% of the Class A membership units of the limited liability company that owned the Fort Lauderdale and Boston 2 development property investments with a Profits Interest. On February 21, 2020, the Company purchased 100% of the Class A membership units of the limited liability company that owned the Atlanta 4 development property investment with a Profits Interest. On April 10, 2020 and May 6, 2020, respectively, the Company purchased 100% of the Class A membership units of the limited liability companies that owned the Raleigh and Jacksonville 3 development property investments with a Profits Interest. Additionally, on June 30, 2020, the Company purchased 100% of the Class A membership units of the limited liability companies that owned the Baltimore 1, Louisville 2, Minneapolis 1, Minneapolis 2, and Minneapolis 3 development property investments with a Profits Interest. On July 15, 2020, the Company acquired 100% of the Class A membership units of the LLC that owned the New York City 2 development property investment. On July 31, 2020, the Company acquired 100% of the Class A membership units of the LLCs that own the Orlando 3 and Denver 1 development property investments. ​ 2019 Activity ​ On March 8, 2019, the Company purchased 100% of the Class A membership units of the limited liability company that owned the New Haven development property investment with a Profits Interest. On July 2, 2019, the Company acquired all of the interests in the entity that owned the property securing the Miami construction loan. On August 16, 2019, the Company purchased 100% of the Class A membership units of the limited liability company that owned the Jacksonville 2 development property investment with a Profits Interest. On September 17, 2019, the Company purchased 100% of the Class A membership units of the limited liability companies that owned the Miami 4, Miami 5, Miami 6, Miami 7 and Miami 8 bridge investments with a Profits Interest. Accordingly, as of the dates of acquisition, the Company wholly owns and consolidates these investments in the accompanying consolidated financial statements. The acquisition date basis of these investments of $138.9 million is primarily comprised of the development property investment or bridge investment at fair value of $125.7 million and the cash consideration of $10.5 million, which is inclusive of paid and accrued transaction costs. The Company allocated the basis based on the relative fair value of the tangible and intangible assets acquired. Intangible assets consisted of in-place leases, which aggregated to $5.1 million at the time of the acquisitions. The estimated life of these in-place leases was 12 months. ​ As of December 31, 2019, the basis of the Miami investment acquired on July 2, 2019 was presented in land, $3.9 million, and construction-in-progress, $16.5 million within Self-storage real estate owned, net, in the table below. The facility was placed into service on February 10, 2020. ​ The Company evaluated the purchases under ASU 2017-01 and concluded that the transactions consisted of a single identifiable asset or a group of similar identifiable assets that represent substantially all of the fair value of the gross assets acquired. Therefore, these transactions do not constitute the purchase of a business and have been treated as asset acquisitions. In accordance with ASU 2017-01, as of the respective acquisition dates, the Company’s basis in the self-storage real estate owned is recorded at cost (generally equal to the cash consideration paid, assumed liabilities, if applicable, and the funded loan balance, net of unamortized origination fees), plus unrealized gains recorded at the date of acquisition. The allocation to the basis of the assets acquired is based on their relative fair values. ​ The following table shows the components of the real estate investments as presented in the Company’s accompanying Consolidated Balance Sheets as of September 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ December 31, 2019 Land ​ $ 72,262 ​ $ 29,430 Building and improvements ​ ​ 448,796 ​ ​ 186,295 In-place leases ​ ​ 16,128 ​ ​ 8,629 Property equipment ​ ​ 217 ​ ​ 122 Construction-in-progress ​ ​ — ​ ​ 16,460 Accumulated depreciation and amortization ​ ​ (23,410) ​ ​ (10,092) Self-storage real estate owned, net ​ $ 513,993 ​ $ 230,844 ​

FAIR VALUE OF FINANCIAL INSTRUM

FAIR VALUE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2020
FAIR VALUE OF FINANCIAL INSTRUMENTS [Abstract]
FAIR VALUE OF FINANCIAL INSTRUMENTS	4. FAIR VALUE OF FINANCIAL INSTRUMENTS Estimates inherent in the determination of fair value inevitably involve assumptions about future events and actual results may differ from those estimates. The COVID-19 pandemic has adversely impacted and is likely to further adversely impact the self-storage industry, generally, and the Company’s operations and value, specifically. Specific negative impacts could include lateness and, ultimately, uncollectibility of an increased number of rental payments, the length of time required to lease-up recently-constructed properties and the ability to increase rental rates, all of which negatively impact revenue from properties and/or the value of our investments. The full extent to which the pandemic will directly or indirectly impact the Company’s business, results of operations and financial condition will depend on future developments that are difficult to predict. These developments include, but are not limited to, the duration and extent of continued spread of the novel coronavirus, the severity of the virus, the actions to contain the virus or address its impact, governmental actions to contain the spread of the virus and to respond to economic deterioration caused by the pandemic (including rapidly accelerating unemployment rates, business bankruptcies, dislocation of equity and debt markets and a dramatic decline in consumer spending and gross domestic product), and how quickly and to what extent normal economic and operating conditions can resume. Management has considered the foregoing factors and the impact of the pandemic, generally, on the economy, the self-storage industry and the Company and adjusted certain estimates, where relevant, used in the preparation of its fair value measurements. ​ The fair value option under ASC 825-10 allows companies to elect to report selected financial assets and liabilities at fair value. The Company has elected the fair value option of accounting for its development property investments in order to provide stockholders and others who rely on the Company’s financial statements with a more complete and accurate understanding of the Company’s economic performance, including its revenues and value inherent in its equity participation in self-storage development projects. ​ The Company applies ASC 820, Fair Value Measurement ​ Level 1- Quoted prices for identical assets or liabilities in an active market. Level 2- Financial assets and liabilities whose values are based on the following: (i) Quoted prices for similar assets or liabilities in active markets; (ii) Quoted prices for identical or similar assets or liabilities in non-active markets; (iii) Pricing models whose inputs are derived principally from or corroborated by observable market data for substantially the full term of the asset or liability. Level 3- Prices or valuation techniques based on inputs that are both unobservable and significant to the overall fair value measurement. ​ Financial assets and liabilities that are not measured at fair value on a recurring basis are cash, other loans, receivables, the secured revolving credit facility, term loans and payables and their carrying values approximate their fair values due to their short-term nature or due to a variable interest rate. Cash, receivables, and payables are categorized as Level 1 instruments in the measurement of fair value. Other loans, the secured revolving credit facility and term loans are categorized as Level 2 instruments in the measurement of fair value as the fair values of these investments are determined using a discounted cash flow model with inputs from third-party pricing sources and similar instruments. ​ As discussed in Note 8, Risk Management and Use of Financial Instruments, ​ Credit valuation adjustments are incorporated to appropriately reflect the Company's and the counterparty's respective nonperformance risk in the fair value measurements. In adjusting the fair value of the derivative contracts for the effect of nonperformance risk, the Company has considered the impact of netting and any applicable credit enhancements, such as collateral postings, thresholds, mutual puts and guarantees. ​ The following table summarizes the instruments measured at fair value on a recurring basis categorized in Level 3 of the fair value hierarchy and the valuation techniques and inputs used to measure their fair value. ​ ​ ​ ​ ​ ​ Instrument ​ Valuation technique and assumptions ​ Hierarchy classification ​ ​ ​ ​ ​ Development property investments with a profits interest ​ Valuations are determined using an Income Approach analysis, using the discounted cash flow method model, capturing the prepayment penalty / call price schedule as applicable. The valuation models are calibrated to the total investment net drawn amount as of the issuance date factoring in the value of the Profits Interests. Typically, the calibration is done on an investment level basis. In certain instances, the Company may acquire a portfolio of investments in which case the calibration is done on an aggregate basis to the aggregate net drawn amount as of the date of issuance. ​ Level 3 ​ The Company’s development property investments are valued using two different valuation techniques. The first valuation technique is an income approach analysis of the debt instrument components of the Company’s investments. The second valuation technique is an OPM that is used to determine the fair value of any Profits Interests associated with an investment. The valuation models are calibrated to the total investment net drawn amount as of the issuance date factoring in the value of the Profits Interests. At the issuance date of each development property investment, generally the value of the property underlying such investment approximates the sum of the net investment drawn amount plus the developer’s equity investment. Typically the calibration is done on an investment level basis. To the extent investments are entered into on a portfolio basis, the valuation models are calibrated on an aggregate basis to the aggregate net investment proceeds using the overall implied internal rate of return using a discounted cash flow for each investment. ​ For development property investments with a Profits Interest, at a certain stage of construction, the OPM incorporates an adjustment to measure entrepreneurial profit. Entrepreneurial profit is a monetary return above total construction costs that provides compensation for the risk of a development project. Under this method, the value of each property is estimated based on the cost incurred to date, plus an estimated earned entrepreneurial profit. Total entrepreneurial profit is estimated as the difference between the projected value of a property at stabilization and the total development costs, including land, building improvements, and lease-up costs. Utilizing information obtained from the market coupled with the Company’s own experience, the Company has estimated that in most cases, approximately one-third of the entrepreneurial profit is earned during the construction period beginning when construction is approximately 40% complete and ending when construction is substantially complete, and approximately two-thirds of the entrepreneurial profit is earned from when construction is substantially complete through stabilization. For the three development property investments that were 40% complete but for which construction was not substantially complete at September 30, 2020, the Company has estimated the entrepreneurial profit adjustment to the enterprise value input used in the OPM to be equal to one-third of the estimated entrepreneurial profit, allocated on a straight-line basis. Seventeen development property investments, not including the properties reported as self-storage real estate owned, had reached substantial construction completion and/or received a certificate of occupancy at September 30, 2020. For the Company’s development property investments at substantial construction completion, a discounted cash flow model, based on periodically updated estimates of rental rates, occupancy, occupancy trends and operating expenses, is the primary method for projecting value of a project. The Company also will consider inputs such as appraisals which differ from the developer’s equity investment, bona fide third-party offers to purchase development projects, sales of development projects, or sales of comparable properties in its markets. ​ Level 3 Fair Value Measurements ​ The following tables summarize the significant unobservable inputs the Company used to value its investments categorized within Level 3 as of September 30, 2020 and December 31, 2019. These tables are not intended to be all-inclusive, but instead to capture the significant unobservable inputs relevant to the Company’s determination of fair values. The significant unobservable inputs associated with the Philadelphia and Houston investments are not included as the fair value was determined based on the fair value of the underlying collateral. The fair value of the underlying collateral was determined, in part, by using a market comparable approach and an income approach based on a capitalization rate within the range provided below for capitalization rates associated with development property investments with a profits interest. ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2020 ​ ​ Unobservable Inputs Primary Valuation ​ ​ ​ ​ ​ Weighted Techniques ​ Input ​ Estimated Range ​ Average Income approach analysis ​ Market yields/discount rate ​ 6.94 - 9.16% ​ 8.10% ​ ​ Exit date (a) ​ 0.83 - 5.94 years ​ 3.65 years ​ ​ ​ ​ ​ ​ ​ Option pricing model ​ Volatility ​ 67.03 - 96.75% ​ 78.51% ​ ​ Exit date (a) ​ 0.83 - 5.94 years ​ 3.65 years ​ ​ Capitalization rate (b) ​ 5.25 - 5.50% ​ 5.43% ​ ​ Discount rate (b) ​ 8.25 - 8.50% ​ 8.43% (a) The exit dates for the development property investments are generally the estimated date of stabilization of the underlying property. (b) Twenty properties were 40% - 100% complete, thus requiring a capitalization rate and/or discount rate to derive entrepreneurial profit, which are used to derive the enterprise value input to the OPM. Capitalization rates are estimated based on current data derived from independent sources in the markets in which the Company holds investments. ​ ​ ​ ​ ​ ​ ​ As of December 31, 2019 ​ ​ Unobservable Inputs Primary Valuation ​ ​ ​ ​ ​ Weighted Techniques ​ Input ​ Estimated Range ​ Average Income approach analysis ​ Market yields/discount rate ​ 6.89 - 10.16% ​ 8.39% ​ ​ Exit date (a) ​ 1.50 - 6.69 years ​ 3.40 years ​ ​ ​ ​ ​ ​ ​ Option pricing model ​ Volatility ​ 60.95 - 93.83% ​ 73.24% ​ ​ Exit date (a) ​ 1.50 - 6.69 years ​ 3.40 years ​ ​ Capitalization rate (b) ​ 4.75 - 5.75% ​ 5.46% ​ ​ Discount rate (b) ​ 7.75 - 8.75% ​ 8.46% (a) The exit dates for the development property investments are generally the estimated date of stabilization of the underlying property. (b) Thirty-eight properties were 40% - 100% complete, thus requiring a capitalization rate and/or discount rate to derive entrepreneurial profit, which are used to derive the enterprise value input to the OPM. Capitalization rates are estimated based on current data derived from independent sources in the markets in which the Company holds investments. ​ The fair value measurements are sensitive to changes in unobservable inputs. A change in those inputs to a different amount might result in a significantly higher or lower fair value measurement. The following provides a discussion of the impact of changes in each of the unobservable inputs on the fair value measurement. ​ Market yields - changes in market yields and discount rates, each in isolation, may change the fair value of certain of the Company’s investments. Generally, an increase in market yields or discount rates may result in a decrease in the fair value of certain of the Company’s investments. The following fluctuations in the market yields/discount rates would have had the following impact on the fair value of our investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Increase (decrease) in fair value of investments Change in market yields/discount rates (in millions) ​ September 30, 2020 ​ December 31, 2019 Up 25 basis points ​ $ (1.1) ​ $ (2.1) Down 25 basis points, subject to a minimum yield/rate of 10 basis points ​ ​ 0.5 ​ ​ 2.2 ​ ​ ​ ​ ​ ​ ​ Up 50 basis points ​ ​ (2.2) ​ ​ (4.2) Down 50 basis points, subject to a minimum yield/rate of 10 basis points ​ ​ 0.5 ​ ​ 4.5 ​ Capitalization rate - changes in capitalization rate, in isolation and all else equal, may change the fair value of certain of the Company’s development investments containing Profits Interests. Generally an increase in the capitalization rate assumption may result in a decrease in the fair value of the Company’s investments. The following fluctuations in the capitalization rates would have had the following impact on the fair value of the Company’s investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Increase (decrease) in fair value of investments Change in capitalization rates (in millions) ​ September 30, 2020 ​ December 31, 2019 Up 25 basis points ​ $ (4.8) ​ $ (10.2) Down 25 basis points ​ ​ 5.2 ​ ​ 11.1 ​ ​ ​ ​ ​ ​ ​ Up 50 basis points ​ ​ (9.5) ​ ​ (19.4) Down 50 basis points ​ ​ 11.0 ​ ​ 23.4 ​ Exit date - changes in exit date, in isolation and all else equal, may change the fair value of certain of the Company’s investments that have Profits Interests. Generally, an acceleration in the exit date assumption may result in an increase in the fair value of the Company’s investments. ​ Volatility - changes in volatility, in isolation and all else equal, may change the fair value of certain of the Company’s investments that have Profits Interests. Generally, an increase in volatility may result in an increase in the fair value of the Profits Interests in certain of the Company’s investments. ​ Operating cash flow projections - changes in the operating cash flow projections of the underlying self-storage facilities, in isolation and all else equal, may change the fair value of certain of the Company’s investments that have Profits Interests. Generally, an increase in operating cash flow projections may result in an increase in the fair value of the Profits Interests in certain of the Company’s investments. ​ The Company also evaluates the impact of changes in instrument-specific credit risk in determining the fair value of investments. There were no significant gains or losses attributable to changes in instrument-specific credit risk in the three and nine months ended September 30, 2020 and 2019. ​ Due to the inherent uncertainty of determining the fair value of investments that do not have a readily available market value, the fair value of the Company’s investments may fluctuate from period to period. Additionally, the fair value of the Company’s investments may differ significantly from the values that would have been used had a ready market existed for such investments and may differ materially from the values that the Company may ultimately realize. Further, such investments are generally subject to legal and other restrictions on resale or otherwise are less liquid than publicly traded securities. If the Company were required to liquidate an investment in a forced or liquidation sale, it could realize significantly less than the value at which the Company has recorded it. In addition, changes in the market environment and other events that may occur over the life of the investments may cause the gains or losses ultimately realized on these investments to be different than the unrealized gains or losses reflected in the valuations currently assigned. ​ The following tables present changes in investments that use Level 3 inputs: ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2019 $ 549,684 Realized gains ​ ​ — Unrealized losses ​ ​ (5,630) Fundings of principal and change in unamortized origination fees ​ ​ 26,354 Repayments of loans ​ ​ (13,878) Payment-in-kind interest ​ ​ 15,219 Reclassification of self-storage real estate owned ​ ​ (255,495) Net transfers in or out of Level 3 ​ ​ — Balance at September 30, 2020 ​ $ 316,254 ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2018 ​ $ 457,947 Unrealized gains ​ ​ 28,847 Fundings of principal and change in unamortized origination fees ​ ​ 126,100 Repayments of loans ​ ​ (361) Payment-in-kind interest ​ ​ 22,069 Reclassification of self-storage real estate owned ​ ​ (125,715) Net transfers in or out of Level 3 ​ ​ — Balance at September 30, 2019 ​ $ 508,887 ​ As of September 30, 2020 and December 31, 2019, the total net unrealized appreciation on the investments that use Level 3 inputs was $36.3 million and $76.8 million, respectively. ​ For the three and nine months ended September 30, 2020 and 2019, substantially all of the net unrealized gain (loss) on investments in the Company’s Consolidated Statements of Operations were attributable to unrealized gains (losses) relating to the Company’s Level 3 assets still held as of the respective balance sheet date. ​ Transfers between levels, if any, are recognized at the beginning of the quarter in which the transfers occur.

INVESTMENT IN SELF-STORAGE REAL

INVESTMENT IN SELF-STORAGE REAL ESTATE VENTURE	9 Months Ended
	Sep. 30, 2020
INVESTMENT IN SELF-STORAGE REAL ESTATE VENTURE [Abstract]
INVESTMENT IN SELF-STORAGE REAL ESTATE VENTURE	5. INVESTMENT IN SELF-STORAGE REAL ESTATE VENTURE On March 7, 2016, the Company, through its Operating Company, entered into the Limited Liability Company Agreement (the “JV Agreement”) of Storage Lenders LLC, a Delaware limited liability company, to form a real estate venture (the “SL1 Venture”) with HVP III Storage Lenders Investor, LLC (“HVP III”), an investment vehicle managed by Heitman Capital Management LLC (“Heitman”). The SL1 Venture was formed for the purpose of providing capital to developers of self-storage facilities identified and underwritten by the Company. Upon formation, HVP III committed $110.0 million for a 90% interest in the SL1 Venture, and the Company committed $12.2 million for a 10% interest. On March 31, 2016, the Company contributed to the SL1 Venture three of its existing development property investments with a Profits Interest located in Miami and Fort Lauderdale, Florida that were not yet under construction. These investments had an aggregate committed principal amount of approximately $41.9 million and an aggregate drawn balance of $8.1 million. In exchange, the Company’s initial funding commitment of $12.2 million was reduced by $8.1 million, representing the Company’s initial “Net Invested Capital” balance as defined in the JV Agreement. The Company accounted for this contribution in accordance with ASC 845, Nonmonetary Transactions As of December 31, 2018, the SL1 Venture had closed on eight new development property investments with a Profits Interest with an aggregate commitment amount of approximately $81.4 million, bringing the total aggregate commitment of the SL1 Venture’s investments to $123.3 million. Accordingly, HVP III’s total commitment for a 90% interest in the SL1 Venture is $111.0 million, and the Company’s total commitment for a 10% interest in the SL1 Venture is $12.3 million. Under the JV Agreement, the Company receives a priority distribution (after debt service and any reserve but before any other distributions) out of operating cash flow and residual distributions based upon 1% of the committed principal amount of loans made by the SL1 Venture, exclusive of the loans contributed to the SL1 Venture by the Company. Operating cash flow of the SL1 Venture (after debt service, reserves and the foregoing priority distributions) is distributed in accordance with capital commitments. Residual cash flow from capital and other events (after debt service, reserves and priority distributions) will be distributed (i) pro rata in accordance with capital commitments (its “Percentage Interest”) until each member has received a return of all capital contributed; (ii) pro rata in accordance with each member’s Percentage Interest until Heitman has achieved a 14% internal rate of return; (iii) to Heitman in an amount equal to its Percentage Interest less 10% and to the Company in an amount equal to the Company’s Percentage Interest plus 10% until Heitman has achieved a 17% internal rate of return; (iv) to Heitman in an amount equal to its Percentage Interest less 20% and to the Company in an amount equal to the Company’s Percentage Interest plus 20% until Heitman has achieved a 20% internal rate of return; and (v) any excess to Heitman in an amount equal to its Percentage Interest less 30% and to the Company in an amount equal to the Company’s Percentage Interest plus 30%. However, the Company will not be entitled to any such promoted interest prior to the earlier to occur of the third anniversary of the JV Agreement and Heitman receiving distributions to the extent necessary to provide Heitman with a 1.48 multiple on its contributed capital. Since the allocation of cash distributions and liquidating distributions are determined as described in the preceding paragraph, the Company has applied the hypothetical-liquidation-at-book-value (“HLBV”) method to allocate the earnings of the SL1 Venture. Under the HLBV approach, the Company’s share of the investee’s earnings or loss is calculated by: ● The Company’s capital account at the end of the period assuming that the investee was liquidated or sold at book value, plus ● Cash distributions received by the Company during the period, minus ● Cash contributions made by the Company during the period, minus ● The Company’s capital account at the beginning of the period assuming that the investee were liquidated or sold at book value. ​ On January 28, 2019, the SL1 Venture purchased 100% of the Class A membership units of the LLCs that owned the Atlanta 1, Jacksonville, Atlanta 2, and Denver development property investments with a Profits Interest. These purchases increased the SL1 Venture’s ownership interest on each development property investment from 49.9% to 100%. The SL1 Venture now wholly owns the self-storage properties through these LLCs. The acquisition date basis of these investments of $57.2 million is primarily comprised of the development property investment at fair value and the cash consideration paid. ​ On February 27, 2019, the SL1 Venture closed on a $36.1 million term loan secured by these four owned properties that bears interest at LIBOR plus 2.15% and matures on February 27, 2022 . The SL1 Venture distributed $19.0 million and $2.1 million to HVP III and the Company, respectively, of these debt proceeds. In April 2019, the SL1 Venture entered into an interest rate swap to fix the interest rate on the variable rate term loan. The SL1 Venture interest rate swap bears a notional amount of ​ On September 17, 2019, the SL1 Venture’s loan related to the Washington D.C. development property investment was repaid in full through a refinancing initiated by the SL1 Venture’s partner. The SL1 Venture distributed $15.5 million and $1.7 million to HVP III and the Company, respectively, of these loan repayment proceeds. The Washington D.C. investment at September 30, 2020, represents the SL1 Venture’s 49.9% Profits Interest which was retained during the transaction. ​ On November 7, 2019, the SL1 Venture purchased 100% of the Class A membership units of the LLC that owned the Raleigh development property investment with a Profits Interest. This purchase increased the SL1 Venture’s ownership interest on this development property investment from 49.9% to 100%. The SL1 Venture now wholly owns the self-storage property through this LLC. The acquisition date basis of this investment of $9.7 million is primarily comprised of the development property investment at fair value. ​ On January 31, 2020, the SL1 Venture closed on a $3.2 million term loan secured by the Raleigh owned property that bears interest at LIBOR plus 2.15% and matures on February 27, 2022 . The SL1 Venture distributed $2.7 million and $0.3 million to HVP III and the Company, respectively, of these debt proceeds. ​ On March 4, 2020 the SL1 Venture’s loans related to the Miami 1, Miami 2, and Fort Lauderdale development property investments were repaid in full through a refinancing initiated by the SL1 Venture’s development partner. The SL1 Venture distributed $36.5 million and $4.1 million to HVP III and the Company, respectively, of these loan repayment proceeds. The Miami 1, Miami 2, and Fort Lauderdale investments at September 30, 2020, represents the SL1 Venture’s 49.9% Profits Interest which was retained during the transaction. ​ On June 24, 2020 the SL1 Venture purchased 100% of the Class A membership units of the LLC that owned the Columbia development property investment with a Profits Interest. This purchase increased the SL1 Venture’s ownership interest on this development property investment from 49.9% to 100%. The SL1 Venture now wholly owns the self-storage property through this LLC. The acquisition date basis of this investment of $10.3 million is primarily comprised of the development property investment at fair value. ​ The SL1 Venture has elected the fair value option of accounting for its development property investments with a Profits Interest, which are equity method investments of the SL1 Venture. The assumptions used to value the SL1 Venture’s investments are materially consistent with those used to value the Company’s investments. As of September 30, 2020, the SL1 Venture had five development property investments with a Profits Interest as described in more detail in the table below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Metropolitan ​ ​ ​ ​ ​ ​ ​ Remaining ​ ​ ​ ​ ​ Statistical Area ​ Total Investment ​ Funded ​ Unfunded ​ ​ ​ Closing Date ​ ("MSA") ​ Commitment ​ Investment (1) ​ Commitment ​ Fair Value 5/14/2015 ​ Miami 1 (2)(3)(4) ​ $ — ​ $ — ​ $ — ​ $ 1,638 5/14/2015 ​ Miami 2 (2)(3)(4) ​ ​ — ​ ​ — ​ ​ — ​ ​ 1,702 9/25/2015 ​ Fort Lauderdale (2)(3)(4) ​ ​ — ​ ​ — ​ ​ — ​ ​ 4,211 4/15/2016 ​ Washington DC (3)(4) ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,727 7/21/2016 ​ New Jersey (3) ​ ​ 7,828 ​ ​ 7,471 ​ ​ 357 ​ ​ 8,880 ​ ​ Total ​ $ 7,828 ​ $ 7,471 ​ $ 357 ​ $ 20,158 ​ ​ (1) Represents principal balance of loan gross of origination fees. The principal balance includes interest accrued on the investment. (2) These development property investments (having approximately $8.1 million of outstanding principal at contribution) were contributed to the SL1 Venture on March 31, 2016 by the Company. (3) Certificate of occupancy had been received as of September 30, 2020. See Note 4, Fair Value of Financial Instruments , for information regarding recognition of entrepreneurial profit. (4) The SL1 Venture’s loan was repaid in full through a refinancing initiated by the SL1 Venture’s partner. This investment represents the SL1 Venture’s 49.9% Profits Interest which was retained during the transaction. ​ As of December 31, 2019, the SL1 Venture had six development property investments with a Profits Interest as described in more detail in the table below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Metropolitan ​ ​ ​ ​ ​ ​ ​ Remaining ​ ​ ​ ​ ​ Statistical Area ​ Total Investment ​ Funded ​ Unfunded ​ ​ ​ Closing Date ​ ("MSA") ​ Commitment ​ Investment (1) ​ Commitment ​ Fair Value 5/14/2015 ​ Miami 1 (2)(3) ​ $ 13,867 ​ $ 13,114 ​ $ 753 ​ $ 16,222 5/14/2015 ​ Miami 2 (2)(3) ​ ​ 14,849 ​ ​ 14,519 ​ ​ 330 ​ ​ 16,588 9/25/2015 ​ Fort Lauderdale (2)(3) ​ ​ 13,230 ​ ​ 12,899 ​ ​ 331 ​ ​ 17,156 4/15/2016 ​ Washington DC (3)(4) ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,339 7/21/2016 ​ New Jersey (3) ​ ​ 7,828 ​ ​ 7,357 ​ ​ 471 ​ ​ 9,036 9/28/2016 ​ Columbia (3) ​ ​ 9,199 ​ ​ 9,073 ​ ​ 126 ​ ​ 10,445 ​ ​ Total ​ $ 58,973 ​ $ 56,962 ​ $ 2,011 ​ $ 72,786 (1) Represents principal balance of loan gross of origination fees. The principal balance includes interest accrued on the investment. (2) These development property investments (having approximately $8.1 million of outstanding principal at contribution) were contributed to the SL1 Venture on March 31, 2016 by the Company. (3) Certificate of occupancy had been received as of December 31, 2019. See Note 4, Fair Value of Financial Instruments , for information regarding recognition of entrepreneurial profit. (4) The SL1 Venture’s loan was repaid in full through a refinancing initiated by the SL1 Venture’s partner. This investment represents the SL1 Venture’s 49.9% Profits Interest which was retained during the transaction. ​ As of September 30, 2020, the SL1 Venture had total assets of $95.3 million and total liabilities of $41.0 million. During the three and nine months ended September 30, 2020, the SL1 Venture had a loss of $(1.4) million and $(3.0) million, of which ($0.1) million and $(0.3) million were allocated to the Company and ($1.3) million and $(2.7) million were allocated to HVP III, respectively, under the HLBV method. At September 30, 2020, $0.2 million of transaction expenses were included in the carrying amount of the Company’s investment in the SL1 Venture. Additionally, the Company may from time to time make advances to the SL1 Venture. At September 30, 2020 and December 31, 2019, the Company had none and $0.3 million, respectively, in advances to the SL1 Venture, and the related interest on these advances are classified in equity in earnings from unconsolidated self-storage real estate venture in the Consolidated Statements of Operations. ​ Under the JV Agreement, Heitman and the Company will seek to obtain and, if obtained, will share joint rights of first refusal to acquire self-storage facilities that are the subject of development property investments made by the SL1 Venture. Additionally, so long as the Company, through its operating subsidiary, is a member of the SL1 Venture and the SL1 Venture holds any assets, the Company will not make any investment of debt or equity or otherwise, directly or indirectly, in one or more new joint ventures or similar programs for the purposes of funding or providing development loans or financing, directly or indirectly, for the development, construction or conversion of self-storage facilities, in each case without first offering such opportunity to Heitman to participate on substantially the same terms as those set forth in the JV Agreement, either through the SL1 Venture or a newly formed real estate venture. ​ The JV Agreement permits Heitman to cause the Company to repurchase from Heitman its Developer Equity Interests (as defined in the JV Agreement) in certain limited circumstances. Under the JV Agreement, if a developer causes to be refinanced a self-storage facility with respect to which the SL1 Venture has made a development property investment and such refinancing does not coincide with a sale of the underlying self-storage facility, then at any time after the fourth anniversary of the commencement of the SL1 Venture, Heitman may either put to the Company its share of the Developer Equity Interests in respect of each such development property investment, or sell Heitman’s Developer Equity Interests to a third party. On September 30, 2020, Heitman notified the Company of its intent to exercise its put of its Developer Equity Interests in four properties. As of September 30, 2020, the expected exercise price of Heitman’s puts would result in a loss on settlement of these puts for the Company. Accordingly, the Company recognized a loss of $1.9 million on these puts for the three months and nine months ended September 30, 2020. Based on the Company’s assessment as of December 31, 2019, the likelihood of loss on the puts was deemed remote and therefore no value was assigned to the puts as of that date. ​ The Company is the managing member of the SL1 Venture and manages and administers (i) the day-to-day business and affairs of the SL1 Venture and any of its acquired properties and (ii) loan servicing and other administration of the approved development property investments. The Company will be paid a monthly expense reimbursement amount by the SL1 Venture in connection with its role as managing member, as set forth in the JV Agreement. Heitman may remove the Company as the managing member of the SL1 Venture if it commits an event of default (as defined in the JV Agreement), if it undergoes a change of control (as defined in the JV Agreement), or if it becomes insolvent. ​ Heitman approves all “Major Decisions” of the SL1 Venture, as defined in the JV Agreement, including, but not limited to, each investment of capital, the incurrence of any indebtedness, the sale or other disposition of assets of the SL1 Venture, the replacement of the managing member, the acceptance of new members into the SL1 Venture and the liquidation of the SL1 Venture.

VARIABLE INTEREST ENTITIES

VARIABLE INTEREST ENTITIES	9 Months Ended
	Sep. 30, 2020
VARIABLE INTEREST ENTITIES [Abstract]
VARIABLE INTEREST ENTITIES	6. VARIABLE INTEREST ENTITIES ​ Operating Company Investment The Company has determined that its investment in the Operating Company represents a VIE and that the Company is the primary beneficiary of the VIE. In determining whether the Company is the primary beneficiary of a VIE, management considers both qualitative and quantitative factors, including but not limited to, those activities that most significantly impact the VIE's economic performance and which party controls such activities. Accordingly, management has determined that the Company’s ownership of over 90% of the outstanding OC Units and corresponding ability to direct the activities that most significantly impact the VIE’s economic performance along with the lack of substantive kick-out right or substantive participating rights indicates that the company is the primary beneficiary of the VIE, therefore, the Company consolidates the Operating Company. ​ Development Property Investments ​ The Company holds variable interests in its development property investments. The Company has determined that these investees qualify as VIEs because the entities do not have enough equity to finance their activities without additional subordinated financial support. In determining whether the Company is the primary beneficiary of the development property VIEs, the Company identified the activities that most significantly impact the development property VIEs’ economic performance. Such activities are (1) managing the construction and operations of the project, (2) selecting the property manager, (3) making financing decisions, (4) authorizing capital expenditures and (5) disposing of the property. Although the Company has certain participating and protective rights, it does not have the power to direct the activities that most significantly impact the development property VIEs’ economic performance and is not the primary beneficiary; therefore, the Company does not consolidate the development property VIEs. ​ The Company has recorded assets of $316.3 million and $549.7 million at September 30, 2020 and December 31, 2019, respectively, for its variable interest in the development property investment VIEs which is included in the development property investments at fair value line items in the Consolidated Balance Sheets. The Company’s maximum exposure to loss as a result of its involvement with the development property investment VIEs is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ December 31, 2019 Assets recorded related to VIEs ​ $ 316,254 ​ $ 549,684 Unfunded loan commitments to VIEs ​ ​ 52,450 ​ ​ 136,104 Maximum exposure to loss ​ $ 368,704 ​ $ 685,788 ​ The Company has a construction completion guaranty from the managing members of the development property VIEs or individual affiliates/owners of such managing members. ​ Investment in Real Estate Venture ​ The Company determined that the SL1 Venture qualifies as a VIE because it does not have enough equity to finance its activities without additional subordinated financial support. In determining whether the Company is the primary beneficiary of the entity, the Company identified the activities that most significantly impact the entity’s economic performance. Such activities are (1) approving self-storage development investments and acquiring self-storage properties, (2) managing directly-owned properties, (3) obtaining debt financing, and (4) disposing of investments. Although the Company has certain rights, it does not have the power to direct the activities that most significantly impact the entity’s economic performance and thus is not the primary beneficiary. As such, the Company does not consolidate the entity and accounts for its unconsolidated interest in the SL1 Venture using the equity method of accounting. The Company’s investment in the SL1 Venture is included in the investment in and advances to self-storage real estate venture balance in the Consolidated Balance Sheets, and earnings from the SL1 Venture are included in equity in earnings from unconsolidated real estate venture in the Company’s Consolidated Statements of Operations. The Company’s maximum contribution to the SL1 Venture is $12.3 million, and as of September 30, 2020 and December 31, 2019, the Company’s remaining unfunded commitment to the SL1 Venture is $0.04 million and $0.2 million, respectively. At September 30, 2020 and December 31, 2019, the Company had none and $0.3 million, respectively, in advances to the SL1 Venture.

DEBT

DEBT	9 Months Ended
	Sep. 30, 2020
DEBT [Abstract]
DEBT	7. DEBT A summary of the Company’s debt is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effective ​ Carrying Value as of ​ Maturity Date ​ Interest Rate ​ September 30, 2020 ​ December 31, 2019 Secured revolving credit facility (1) March 24, 2023 ​ 2.65% ​ $ 242,000 ​ $ 162,000 Term Loans: ​ ​ ​ ​ ​ ​ ​ ​ ​ Term loan 1 (2) August 1, 2021 ​ 2.41% ​ ​ 9,150 ​ ​ 9,150 Term loan 2 (2) August 1, 2021 ​ 2.41% ​ ​ 7,125 ​ ​ 7,125 Term loan 3 (2) August 1, 2021 ​ 2.41% ​ ​ 8,625 ​ ​ 8,625 Term loan 4 (2) August 1, 2021 ​ 2.41% ​ ​ 9,188 ​ ​ 9,188 Term loan 5 (2) August 1, 2021 ​ 2.41% ​ ​ 7,087 ​ ​ 7,087 Total Term Loans ​ ​ ​ ​ ​ 41,175 ​ ​ 41,175 Term loan debt issuance costs ​ ​ ​ ​ ​ (202) ​ ​ (384) Net Term Loans ​ ​ ​ ​ ​ 40,973 ​ ​ 40,791 Total debt ​ ​ ​ ​ $ 282,973 ​ $ 202,791 (1) Risk Management and Use of Financial Instruments (2) Risk Management and Use of Financial Instruments ​ Credit Facility ​ On March 26, 2020, the Operating Company entered into a second amended and restated senior secured revolving credit facility of up to $375 million (the “Amended and Restated Credit Facility”) with KeyBank National Association, as administrative agent, KeyBanc Capital Markets Inc. and BMO Capital Markets Corp., as joint lead arrangers, BMO Capital Markets Corp. as syndication agent, Raymond James Bank, N.A. as documentation agent and the other lenders party thereto. Pursuant to an accordion feature, the Operating Company may from time to time increase the commitments under the Amended and Restated Credit Facility up to an aggregate amount of $750 million, subject to, among other things, an absence of default under the Amended and Restated Credit Facility, borrowing base capacity, as well as receiving commitments from lenders for the additional amounts. The Amended and Restated Credit Facility amends and restates the Company’s existing credit facility in all respects. The Operating Company intends to use future borrowings under the Amended and Restated Credit Facility to fund its investments, to make secured or unsecured loans to borrowers in connection with its investments and for general corporate purposes. On March 26, 2020, the Company and certain wholly-owned subsidiaries of the Operating Company (the “Subsidiaries”) entered into a Second Amended and Restated Unconditional Guaranty of Payment and Performance whereby they have agreed to unconditionally guarantee the obligations of the Operating Company under the Amended and Restated Credit Facility. The Amended and Restated Credit Facility is secured by certain of the Company’s investments made through the Subsidiaries, and other subsidiaries of the Operating Company may be added as guarantors from time to time during the term of the Amended and Restated Credit Facility. ​ The Amended and Restated Credit Facility has a scheduled maturity date on March 24, 2023 with two one-year extension options to extend the maturity of the facility to March 26, 2025. Borrowings under the Amended and Restated Credit Facility are secured by three different pools of collateral: the first consisting of the mortgage loans held by the Company or its subsidiaries extended to developers (each a “Mortgage Loan”), the second consisting of certain non-stabilized self-storage properties owned by the Company or one of its wholly owned subsidiaries (the “Non-Stabilized Real Estate Collateral”) and the third consisting of certain stabilized self-storage properties owned by the Company or one of its wholly owned subsidiaries (the “Stabilized Real Estate Collateral” and, together with the Mortgage Loans and the Non-Stabilized Real Estate Collateral, the “Borrowing Base Assets”). ​ The amount available to borrow under the Amended and Restated Credit Facility is limited according to a borrowing base valuation of the assets available as collateral. For loans secured by Mortgage Loans, the borrowing base availability is the lesser of (i) 60% of the outstanding balance of the Mortgage Loans and (ii) the maximum principal amount which would not cause the outstanding loans under the Amended and Restated Credit Facility secured by the Mortgage Loans to be greater than 50% of the underlying real estate assets securing the Mortgage Loans. For loans secured by Non-Stabilized Real Estate Collateral, the borrowing base availability is the lesser of (i) the maximum principal amount that would not cause the outstanding loans under the Amended and Restated Credit Facility secured by Non-Stabilized Real Estate Collateral to be greater than 60% of the as-stabilized value of such Non-Stabilized Real Estate Collateral, (ii) the maximum principal amount which would not cause the outstanding loans and letter of credit liabilities under the Amended and Restated Facility to be greater than 75% of the total development cost of the Non-Stabilized Real Estate Collateral, and (iii) whichever of the following is then applicable: (A) the maximum principal amount that would not cause the ratio of (1) stabilized net operating income from the Non-Stabilized Real Estate Collateral included in the borrowing base divided by (2) an implied debt service coverage amount to be less than 1.35 to 1.00, (B) for any underlying real estate asset securing the Non-Stabilized Real Estate Collateral that has been included in the borrowing base for greater than 18 months , the maximum principal amount which would not cause the ratio of (1) actual adjusted net operating income for the underlying real estate asset securing such Non-Stabilized Real Estate Collateral divided by (2) an implied debt service amount to be less than 0.50 to 1.00, and (C) for any underlying real estate asset securing the Non-Stabilized Real Estate Collateral that has been included in the borrowing base for greater than 30 months , the maximum principal amount which would not cause the ratio of (1) actual adjusted net operating income for the underlying real estate asset securing such Non-Stabilized Real Estate Collateral divided by (2) an implied debt service amount to be less than 1.00 to 1.00. For loans secured by Stabilized Real Estate Collateral, the borrowing base availability is the lesser of (i) the maximum principal amount that would not cause the outstanding loans under the Amended and Restated Credit Facility secured by the underlying real estate asset securing the Stabilized Real Estate Collateral to be greater than 65% of the value of such self-storage property and (ii) the maximum principal amount that would not cause the ratio of (a) actual adjusted net operating income from the underlying real estate asset securing such Stabilized Real Estate Collateral divided by (b) an implied debt service coverage amount to be less than 1.30 to 1.00. Notwithstanding the foregoing, the borrowing base availability will be reduced by certain aggregate operating and interest holdbacks, which must be updated by the Company on a quarterly basis and may be updated by the Company on a monthly basis as leasing at the Company’s properties progresses. All such amounts are subject to approval by the administrative agent. The Amended and Restated Credit Facility includes certain requirements that may limit the borrowing capacity available to the Company from time to time. Under the terms of the Amended and Restated Credit Facility, the outstanding principal balance of the revolving credit loans, swing loans and letter of credit liabilities under the Amended and Restated Credit Facility may not exceed the borrowing base availability. Each loan made under the Amended and Restated Credit Facility will bear interest at either, at the Operating Company’s election, (i) a base rate plus a margin of 1.10%, 1.50% or 2.00% or (ii) LIBOR plus a margin of 2.10%, 2.50% or 3.00% (subject to customary LIBOR replacement protocols), in each case depending on the borrowing base available for such loan. In addition, the Operating Company is required to pay a per diem fee at the rate of either 0.25% or 0.30% per annum, depending on the amount outstanding under the Amended and Restated Credit Facility at the time, times the excess of the sum of the commitments of the lenders, as in effect from time to time, over the outstanding principal amount of revolving credit loans under the Amended and Restated Credit Facility. ​ LIBOR is expected to be discontinued after 2021. The Amended and Restated Credit Facility provides procedures for determining an alternative base rate in the event that LIBOR is discontinued. However, there can be no assurances as to what that alternative base rate will be and whether that base rate will be more or less favorable than LIBOR and any other unforeseen impacts of the potential discontinuation of LIBOR. The Company intends to monitor the developments with respect to the potential phasing out of LIBOR after 2021 and work with its lenders to ensure any transition away from LIBOR will have minimal impact on its financial condition, but can provide no assurances regarding the impact of the discontinuation of LIBOR. ​ The Amended and Restated Credit Facility contains certain customary representations and warranties and financial and other affirmative and negative covenants. The Operating Company’s ability to borrow under the Amended and Restated Credit Facility is subject to ongoing compliance by the Company and the Operating Company with various customary restrictive covenants, including but not limited to limitations on its incurrence of indebtedness, investments, dividends, asset sales, acquisitions, mergers and consolidations and liens and encumbrances. In addition, the Amended and Restated Credit Facility contains certain financial covenants including the following: ​ ● total consolidated indebtedness not exceeding (i) 45% of gross asset value during the period between March 26, 2020 and December 31, 2020, and (ii) 50% of gross asset value during the period between January 1, 2021 through the maturity of the Amended and Restated Credit Facility; ● a minimum fixed charge coverage ratio (defined as the ratio of consolidated adjusted earnings before interest, taxes, depreciation and amortization to consolidated fixed charges) of not less than (i) 1.15 to 1.00 during the period between March 26, 2020 and December 31, 2020, (ii) 1.20 to 1.00 during the period between January 1, 2021 and December 31, 2021 and (iii) 1.40 to 1.00 during the period between January 1, 2022 through the maturity of the Amended and Restated Credit Facility; ● the minimum fixed charge coverage ratio is reduced to 1.05 to 1.00 for no more than one (1) period of up to two (2) consecutive calendar quarters immediately following a Material Acquisition. The period ended September 30, 2020, was subject to this reduced fixed charge coverage ratio as a result of a Material Acquisition. ● a minimum consolidated tangible net worth (defined as gross asset value less total consolidated indebtedness) of $360.5 million plus 75% of the sum of any additional net offering proceeds; ● when aggregate outstanding loans under the Amended and Restated Credit Facility exceed $50 million, unhedged variable rate debt cannot exceed 40% of consolidated total indebtedness; ● liquidity of no less than the greater of (i) future funding commitments of the Company and its subsidiaries for the three months after each date of determination and (ii) $25 million for the period between March 26, 2020 and December 31, 2020 or, on and after January 1, 2021, liquidity of no less than the greater of (i) future funding commitments of the Company and its subsidiaries for the six months following each date of determination and (ii) $25 million; ● a ratio of adjusted consolidated EBITDA determined for the most recently ended calendar quarter, annualized, to debt service for the most recently ended calendar quarter, annualized, of no less than 2.00 to 1; ● a requirement to maintain at all times a minimum of 25 Borrowing Base Assets with an aggregate borrowing base availability of not less than (i) $150 million for the period between March 26, 2020 and December 31, 2020, and (ii) $250 million for the period between January 1, 2021 through the maturity of the Amended and Restated Credit Facility; and ● a minimum borrowing base availability attributable to Non-Stabilized Real Estate Collateral and Stabilized Real Estate Collateral of not less than (i) 20% of total borrowing base availability for the period between March 26, 2020 and December 31, 2020, (ii) 40% of total borrowing base availability for the period between January 1, 2021 and December 31, 2021 and (iii) 60% of total borrowing base availability for the period between January 1, 2022 through the maturity of the Amended and Restated Credit Facility. ​ The Amended and Restated Credit Facility provides for standard events of default, including nonpayment of principal and other amounts when due, non-performance of covenants, breach of representations and warranties, certain bankruptcy or insolvency events, and changes in control. If an event of default occurs and is continuing under the Amended and Restated Credit Facility, the lenders may, among other things, terminate their commitments under the Amended and Restated Credit Facility and require the immediate payment of all amounts owed thereunder. ​ As of September 30, 2020, the Company had $242.0 million outstanding of our $283.8 million of total availability for borrowing under the Amended and Restated Credit Facility. As such, the Company had $41.8 million of remaining capacity for borrowing under the Amended and Restated Credit Facility. As of September 30, 2020, the Company was in compliance with all of its financial covenants of the Amended and Restated Credit Facility. As of September 30, 2020 and December 31, 2019, certain of the Company’s development property investments as described in Note 3, Self-Storage Investment Portfolio Term Loans On August 17, 2018, the Company entered into loan agreements with FirstBank (“FirstBank”) with respect to three term loans in the aggregate principal amount of $24.9 million. On January 18, 2019, the Company entered into a loan agreement with FirstBank with respect to a term loan in the aggregate principal amount of $9.2 million. Additionally, on August 13, 2019, the Company entered into a loan agreement with FirstBank with respect to a term loan in the aggregate principal amount of $7.1 million. These loans are collectively referred to as the “FirstBank Term Loans.” The FirstBank Term Loans are secured by first mortgages on the Company’s five wholly-owned self-storage facilities located in Orlando, Florida, Atlanta, Georgia, Charlotte, North Carolina and New Haven, Connecticut. As a condition to FirstBank providing the FirstBank Term Loans, the Company has agreed to unconditionally guarantee the subsidiaries’ obligations under the FirstBank Term Loans pursuant to guaranty agreements with FirstBank. The FirstBank Term Loans will mature on August 1, 2021. Borrowings under the FirstBank Term Loans bear interest at a floating variable rate of one-month LIBOR plus 2.25%, which is reset monthly. The FirstBank Term Loans are each subject to an interest rate swap to fix the 30-day LIBOR rate. Term Loans 1 to 4 swaps fix 30-day LIBOR at 2.2925% and Term Loan 5 fixes 30-day LIBOR at Risk Management and Use of Financial Instruments The FirstBank Term Loans contain customary representations and warranties and affirmative and negative covenants. The FirstBank Term Loans contain a financial covenant that requires the Operating Company to maintain a debt service coverage ratio of 1.35 to 1. The debt service coverage ratio will be calculated pursuant to the terms of the Credit Facility. FirstBank is a lender under the Credit Facility. The FirstBank Term Loans also contain a covenant that requires the Operating Company to maintain a loan to value ratio on the outstanding balance of the loan that does not exceed the loan to value ratio at closing. The FirstBank Term Loans provide for standard events of default, including nonpayment of principal and other amounts when due, non-performance of covenants, breach of representations and warranties and certain bankruptcy or insolvency events. If an event of default occurs and is continuing under the FirstBank Term Loans, FirstBank may, among other things, terminate its commitments under the FirstBank Term Loans and require the immediate payment of all amounts owed thereunder. The FirstBank Term Loans each contain cross-default provisions with the Credit Facility, pursuant to which an event of default under the FirstBank Term Loans is triggered by the occurrence of an event of default under the Credit Facility that results in acceleration of the outstanding obligations of the Operating Company under the Credit Facility. As of September 30, 2020, the Company was in compliance with all of its financial covenants of the FirstBank Term Loans.

RISK MANAGEMENT AND USE OF FINA

RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS	9 Months Ended
	Sep. 30, 2020
RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS
RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS	8. RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS ​ The Company’s use of derivative instruments is limited to the utilization of interest rate swap and cap agreements to manage interest rate risk exposures and not for speculative purposes. The principal objective of such arrangements is to minimize the risks and/or costs associated with the Company’s operating and financial structure, as well as to hedge specific liabilities. The counterparties to these arrangements are major financial institutions with which the Company and its subsidiaries may also have other financial relationships. The Company is potentially exposed to credit loss in the event of non-performance by these counterparties. However, because of the high credit ratings of the counterparties, the Company does not anticipate that any of the counterparties will fail to meet these obligations as they come due. The Company does not hedge credit or property value market risks. ​ The Company enters into interest rate swap agreements that qualify and are designated as cash flow hedges designed to reduce the impact of interest rate changes on its variable rate debt. Therefore, the interest rate swaps are recorded in the Consolidated Balance Sheets at fair value and the related gains or losses are deferred in stockholders’ equity as accumulated other comprehensive income (loss). These deferred gains and losses are amortized into interest expense during the period or periods in which the related interest payments affect earnings. During the three and nine months ended September 30, 2020 and 2019, the Company was subject to interest rate swaps for all five of its First Bank Term Loans. In addition, the Company was also subject to a $100 million interest rate swap on its Amended and Restated Credit Facility during the three and nine months ended September 30, 2020. The Company formally assesses, both at inception of a hedge and on an on-going basis, whether each derivative is highly-effective in offsetting changes in cash flows of the hedged item. If management determines that a derivative was highly-effective as a hedge, then the Company accounts for the derivative using hedge accounting, pursuant to which gains or losses inherent in the derivative did not impact the Company’s results of operations. If management determines that a derivative was not highly-effective as a hedge or if a derivative ceased to be a highly-effective hedge, the Company will discontinue hedge accounting prospectively and reflect in its statement of operations realized and unrealized gains and losses in respect of the derivative. ​ The Company has agreements with each of its derivative counterparties that contain a provision where if the Company defaults on any of its indebtedness, including default where repayment of the indebtedness has not been accelerated by the lender, then the Company could also be declared in default on its derivative obligations. In addition, the Company has agreements with each of its derivative counterparties that contain a provision where the Operating Partnership could be declared in default on its derivative obligations if repayment of the underlying indebtedness is accelerated by the lender due to the Company’s default on the indebtedness. ​ The following table summarizes the terms and fair values of the Company’s derivative financial instruments designated as hedges as of September 30, 2020 and December 31, 2019, respectively ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Notional Amount ​ ​ ​ ​ ​ ​ ​ Fair Value Hedge Product Hedge Type (1) ​ September 30, 2020 December 31, 2019 Strike ​ Effective Date ​ Maturity ​ September 30, 2020 December 31, 2019 Swap ​ Cash flow ​ $ 9,150 ​ $ 9,150 ​ 2.2925% ​ 6/3/2019 ​ 8/1/2021 ​ $ (165) ​ $ (104) Swap ​ Cash flow ​ ​ 7,125 ​ ​ 7,125 ​ 2.2925% ​ 6/3/2019 ​ 8/1/2021 ​ ​ (129) ​ ​ (81) Swap ​ Cash flow ​ ​ 8,625 ​ ​ 8,625 ​ 2.2925% ​ 6/3/2019 ​ 8/1/2021 ​ ​ (155) ​ ​ (98) Swap ​ Cash flow ​ ​ 9,188 ​ ​ 9,188 ​ 2.2925% ​ 6/3/2019 ​ 8/1/2021 ​ ​ (165) ​ ​ (105) Swap ​ Cash flow ​ ​ 7,087 ​ ​ 7,087 ​ 1.6025% ​ 8/13/2019 ​ 8/1/2021 ​ ​ (87) ​ ​ (5) Swap ​ Cash flow ​ ​ 100,000 ​ ​ — ​ 0.3570% ​ 5/1/2020 ​ 3/24/2023 ​ ​ (408) ​ ​ — ​ ​ ​ ​ $ 141,175 ​ $ 41,175 ​ ​ ​ ​ ​ ​ ​ $ (1,109) ​ $ (393) (1) ​ The Company measures its derivative instruments designated as cash flow hedges at fair value and records them in the balance sheet as either an asset or liability. As of September 30, 2020 and December 31, 2019, all derivative instruments designated as cash flow hedges are included in accounts payable, accrued expenses and other liabilities in the accompanying Consolidated Balance Sheets. The changes in the fair value of the derivatives are reported in accumulated other comprehensive income (loss). Amounts reported in accumulated other comprehensive income (loss) related to derivatives are reclassified to interest expense as interest payments are made on the Company’s variable-rate debt. ​ The following table presents the effect of derivatives designated as hedging instruments on the Consolidated Statements of Comprehensive Income: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives in Cash Flow Hedging Relationships ​ Amount of Gain (Loss) Recognized in Accumulated OCL on Derivative ​ Loss Reclassified from Accumulated OCL into Interest Expense (Income) ​ Location of Loss Reclassified from Accumulated OCL into Expense (Income) Three months ended September 30, ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ ​ ​ ​ Term loan interest rate contracts ​ $ (54) ​ $ (58) ​ $ 238 ​ $ (1) ​ Interest Expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Term loan interest rate contracts ​ $ (1,152) ​ $ (495) ​ $ 461 ​ $ (5) ​ Interest Expense ​ The changes in accumulated other comprehensive income (loss) for the three and nine months ended September 30, 2020 and 2019, are summarized as follows ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ Nine months ended ​ ​ September 30, ​ September 30, ​ ​ ​ 2020 ​ ​ 2019 ​ ​ 2020 ​ ​ 2019 Accumulated other comprehensive income beginning of period ​ $ (1,268) ​ $ (441) ​ $ (393) ​ $ — Other comprehensive income (loss): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrealized gains (losses) on interest rate swaps ​ ​ (54) ​ ​ (58) ​ ​ (1,152) ​ ​ (495) Reclassification of realized losses (gains) on interest rate swaps ​ ​ 238 ​ ​ (1) ​ ​ 461 ​ ​ (5) Amount included in other comprehensive income (loss) ​ ​ 184 ​ ​ (59) ​ ​ (691) ​ ​ (500) Accumulated other comprehensive income (loss) end of period ​ $ (1,084) ​ $ (500) ​ $ (1,084) ​ $ (500) ​ During the next twelve months, the Company estimates that an additional $0.9 million ​ The Company also entered into an interest rate cap agreement in June 2019 with a notional amount of $100 million and a one-month LIBOR interest rate cap of 2.50% , an interest rate cap agreement in March 2020 with a notional amount of $20 million and a one-month LIBOR interest rate cap of 1.50% , and an interest rate cap agreement in May 2020 with a notional amount of $100 million and a one-month LIBOR interest rate cap of 0.50% , collectively the “Interest Rate Cap Agreements”. The Interest Rate Cap Agreements are for a period equal to the term of the Credit Facility at the time of the Interest Rate Cap Agreements. Thus, the June 2019 and March 2020 interest rate cap agreements expire on December 28, 2021 and the May 2020 interest rate cap agreement expires on March 24, 2023 . The Company did not designate the interest rate caps as hedges. As of September 30, 2020 and December 31, 2019, the net carrying amount of the interest rate cap was $0.05 million and $.01 million, respectively and are included in prepaid expenses and other assets in the accompanying Consolidated Balance Sheets. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives Not Designated as Hedging Instruments ​ Amount of Gain (Loss) Recognized in Earnings on Derivative ​ ​ Location of Gain (Loss) Recognized in Income on Derivative Three months ended September 30, ​ 2020 ​ 2019 ​ ​ ​ ​ ​ ​ Credit Facility interest rate cap ​ $ (127) ​ $ (61) ​ ​ Interest Expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Credit Facility interest rate cap ​ $ (208) ​ $ (89) ​ ​ Interest Expense ​

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	9 Months Ended
	Sep. 30, 2020
STOCKHOLDERS' EQUITY [Abstract]
STOCKHOLDERS' EQUITY	9. STOCKHOLDERS’ EQUITY ​ The Company had 23,263,130 and 22,423,283 shares of common stock issued and outstanding , which included 148,961 and 216,165 shares of unvested restricted stock, as of September 30, 2020 and December 31, 2019, respectively. The Company had 139,875 and 133,500 shares of Series A Preferred Stock, par value $0.01 per share (the “Series A Preferred Stock”), issued and outstanding as of September 30, 2020 and December 31, 2019, respectively. The Company also had 1,571,734 shares of 7.00% Series B cumulative redeemable perpetual preferred stock (the “Series B Preferred Stock”) and outstanding as of September 30, 2020 and December 31, 2019. ​ ATM Program ​ On December 18, 2019, the Company entered into a new Equity Distribution Agreement with an aggregate offering price under an at the market equity offering program (the “ATM Program”) of up to $100.0 million. As of September 30, 2020, the Company has issued and sold an aggregate of 4,962,535 shares of common stock at a weighted average price of $21.01 per share under the ATM Program and the Company’s previous ATM Program, receiving net proceeds after commissions and other offering costs of $101.4 million. During the nine months ended September 30, 2020, the Company issued and sold an aggregate of 810,000 shares of common stock at a weighted average price per share of $19.07 under the ATM Program, receiving net proceeds after commissions and other offering costs of $15.0 million. During the three months ended September 30, 2020, the Company did not issue any shares of common stock under the ATM Program. Equity Incentive Plan ​ The Company maintains the Second Amended and Restated 2015 Equity Incentive Plan (the “2015 Equity Incentive Plan”) for the purpose of attracting and retaining directors, executive officers, investment professionals and other key personnel and service providers, including officers and employees of the Manager and other affiliates, and to stimulate their efforts toward the Company’s continued success, long-term growth and profitability. The 2015 Equity Incentive Plan provides for the grant of stock options, share awards (including restricted common stock and restricted stock units), stock appreciation rights, dividend equivalent rights, performance awards, annual incentive cash awards and other equity-based awards, including Long-Term Incentive Plan (“LTIP”) units, which are convertible on a one-for-one basis into Operating Company Units (“OC Units”). ​ Restricted Stock Awards ​ The 2015 Equity Incentive Plan permits the issuance of restricted shares of the Company’s common stock to the Company’s employees and non-employee directors. As of September 30, 2020 and December 31, 2019, 568,911 and 509,509 shares of restricted stock, respectively, had been granted, of which 55,172 vested in 2016, 46,413 vested in 2017, 99,503 vested in 2018, 87,256 vested in 2019, 126,606 vested during the nine months ended September 30, 2020, 65,501 is expected to vest in 2021, 63,207 is expected to vest in 2022, 10,124 is expected to vest in 2023 and 10,129 is expected to vest in 2024. Additionally, 1,666 were forfeited during the year ended December 31, 2019 and 1,667 were forfeited during each of the years ended December 31, 2018 and 2016. ​ A summary of changes in the Company’s restricted shares of common stock for the three and nine months ended September 30, 2020 and 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ Three months ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ ​ average grant ​ ​ ​ average grant ​ ​ Shares ​ date fair value ​ Shares ​ date fair value Unvested at June 30, ​ ​ 150,836 ​ $ 20.93 ​ ​ 208,665 ​ $ 20.35 Granted ​ ​ — ​ ​ - ​ ​ 7,500 ​ ​ 19.84 Vested ​ ​ (1,875) ​ ​ 19.84 ​ ​ — ​ ​ - Forfeited ​ ​ — ​ ​ — ​ ​ — ​ ​ - Unvested at September 30, ​ ​ 148,961 ​ $ 20.94 ​ ​ 216,165 ​ $ 20.34 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended ​ Nine months ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ ​ average grant ​ ​ ​ average grant ​ ​ Shares ​ date fair value ​ Shares ​ date fair value Unvested at December 31, ​ ​ 216,165 ​ $ 20.34 ​ ​ 159,165 ​ $ 18.39 Granted ​ ​ 59,402 ​ ​ 18.00 ​ ​ 145,922 ​ ​ 21.60 Vested ​ ​ (126,606) ​ ​ 18.53 ​ ​ (87,256) ​ ​ 18.95 Forfeited ​ ​ — ​ ​ — ​ ​ (1,666) ​ ​ 18.10 Unvested at September 30, ​ ​ 148,961 ​ $ 20.94 ​ ​ 216,165 ​ $ 20.34 ​ Unvested restricted shares of common stock that vest based on a service condition receive dividends which are nonforfeitable. Awards with a market condition that vest are entitled to dividend equivalent rights for dividends issued during the measurement period contingent upon the achievement of the market condition. ​ Market Condition Restricted Stock Unit Awards ​ Prior to 2020, all unvested shares were earned over the respective vesting period based on a service condition only. During the nine months ended September 30, 2020, the Company also issued 31,243 restricted stock unit awards (“RSUs”) Vesting of restricted stock unit awards with a market condition is based on the Company’s performance as measured by total stockholder return relative to the appreciation of a specified stock index (50%) or a specified peer group (50%) over the measurement period, subject to each participant's continued employment through the conclusion of the measurement period. The fair value of the restricted stock unit awards with a market condition is estimated using a Monte Carlo simulation model and is affected by the grant date, length of the measurement period, and the realized performance and volatility of JCAP and the respective comparison peer group or index. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ Three months ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ ​ average grant ​ ​ ​ average grant ​ ​ RSUs ​ date fair value ​ RSUs ​ date fair value Unvested at June 30, ​ ​ 31,243 ​ $ 26.00 ​ ​ — ​ $ — Granted ​ ​ — ​ ​ — ​ ​ — ​ ​ — Unvested at September 30, ​ ​ 31,243 ​ $ 26.00 ​ ​ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended ​ Nine months ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ ​ average grant ​ ​ ​ average grant ​ ​ Shares ​ date fair value ​ Shares ​ date fair value Unvested at December 31, ​ ​ — ​ $ — ​ ​ — ​ $ — Granted ​ ​ 31,243 ​ ​ 26.00 ​ ​ — ​ ​ — Unvested at September 30, ​ ​ 31,243 ​ $ 26.00 ​ ​ — ​ $ — ​ Stock-based Compensation Expense ​ Expenses related to restricted stock awards and RSUs are charged to compensation expense and are recognized over the respective vesting period (primarily three Stock-based compensation expense for RSUs that vest based on a market condition is based on the fair value of the award and is recorded from the grant date through the conclusion of the required service period. ​ The Company recognized approximately $0.4 million and $0.6 million of stock-based compensation expense for the three months ended September 30, 2020 and 2019, respectively and $1.9 million and $1.7 million for the nine months ended September 30, 2020 and 2019, respectively. As of September 30, 2020 and December 31, 2019, the total unrecognized compensation cost related to the Company’s restricted shares was approximately $3.0 million. This cost is expected to be recognized over the remaining weighted average period of 2.1 years. The Company presents stock-based compensation expense in general and administrative expenses in the Consolidated Statements of Operations. ​ Series A Preferred Stock ​ On July 27, 2016 (the “Effective Date”), the Company entered into a Stock Purchase Agreement (the “Purchase Agreement”) with accounts managed by NexPoint Advisors, L.P., an affiliate of Highland Capital Management, L.P. relating to the issuance and sale, from time to time until the second anniversary of the Effective Date, of up to $125 million in shares of the Company’s Series A Preferred Stock at a price of $1,000 per share (the “Liquidation Value”). The Company has issued all shares of Series A Preferred Stock available for issuance under the Purchase Agreement and the Articles Supplementary classifying the Series A Preferred Stock (the “Articles Supplementary”) except for shares of Series A Preferred Stock issuable as in-kind dividends. ​ The Series A Preferred Stock ranks senior to the shares of the Company’s common stock, par value $0.01 per share (the “Common Stock”), with respect to distribution rights and rights upon liquidation, winding up and dissolution of the Company, on parity with any class or series of capital stock of the Company expressly designated as ranking on parity with the Series A Preferred Stock with respect to distribution rights and rights upon liquidation, winding up and dissolution of the Company, junior to any class or series of capital stock of the Company expressly designated as ranking senior to the Series A Preferred Stock with respect to distribution rights and rights upon liquidation, winding up and dissolution of the Company and junior in right of payment to the Company’s existing and future indebtedness. ​ Holders of Series A Preferred Stock are entitled to a cumulative cash distribution (“Cash Distribution”) equal to (A) 7.0% per annum on the Liquidation Value for the period beginning on the respective date of issuance until the sixth anniversary of the Effective Date, payable quarterly in arrears, (B) 8.5% per annum on the Liquidation Value for the period beginning the day after the sixth anniversary of the Effective Date and for each year thereafter as long as the Series A Preferred Stock remains issued and outstanding, payable quarterly in arrears, and (C) an amount in addition to the amounts in (A) and (B) equal to 5.0% per annum on the Liquidation Value upon the occurrence of certain triggering events (a “Cash Premium”). In addition, the holders of the Series A Preferred Stock will be entitled to a cumulative dividend payable in-kind in shares of Common Stock or additional shares of Series A Preferred Stock, at the election of the holders (the “Stock Dividend”), equal in the aggregate to the lesser of (Y) 25% of the incremental increase in the Company’s book value (as adjusted for equity capital issuances, share repurchases and certain non-cash expenses) plus, to the extent the Company owns equity interests in income-producing real property, the incremental increase in net asset value (provided, however, that no interest in the same real estate asset will be double counted) and (Z) an amount that would, together with the Cash Distribution, result in a 14.0% internal rate of return for the holders of the Series A Preferred Stock from the date of issuance of the Series A Preferred Stock, as set forth in the Articles Supplementary. Triggering events that will trigger the payment of a Cash Premium with respect to a Cash Distribution include: (i) the occurrence of certain change of control events affecting the Company after the third anniversary of the Effective Date, (ii) the Company’s ceasing to be subject to the reporting requirements of Section 13 or Section 15(d) of the Exchange Act, (iii) the Company’s failure to remain qualified as a real estate investment trust, (iv) an event of default under the Purchase Agreement, (v) the failure by the Company to register for resale shares of Common Stock pursuant to the Registration Rights Agreement, (vi) the Company’s failure to redeem the Series A Preferred Stock as required by the Purchase Agreement, or (vii) the filing of a complaint, a settlement with, or a judgment entered by the Securities and Exchange Commission against the Company or any of its subsidiaries or a director or executive officer of the Company relating to the violation of the securities laws, rules or regulations with respect to the business of the Company. ​ Accrued but unpaid Cash Distributions and Stock Dividends on the Series A Preferred Stock will accumulate and will earn additional Cash Distributions and Stock Dividends as calculated above, compounded quarterly. As long as shares of Series A Preferred Stock remain outstanding, the Company is required to maintain a ratio of debt to total tangible assets determined under U.S. generally accepted accounting principles of no more than 0.4:1, measured as of the last day of each fiscal quarter. The Company has complied with this covenant as of September 30, 2020. The Series A Preferred Stock may be redeemed at the Company’s option (i) after five years from the Effective Date at a price equal to 105% of the Liquidation Value per share plus the value of all accumulated and unpaid Cash Distributions and Stock Dividends, and (ii) after six years from the Effective Date at a price equal to 100% of the Liquidation Value per share plus the value of all accumulated and unpaid Cash Distributions and Stock Dividends. In the event of certain change of control events affecting the Company prior to the third anniversary of the Effective Date, the Company must redeem all shares of Series A Preferred Stock for a price equal to (a) the Liquidation Value, plus (b) accumulated and unpaid Cash Distributions and Stock Dividends, plus (c) a make-whole premium designed to provide the holders of the Series A Preferred Stock with a return on the redeemed shares equal to a 14.0% internal rate of return through the third anniversary of the Effective Date. In the event of any liquidation, dissolution or winding up of the Company, the holders of the Series A Preferred Stock shall be entitled to receive an amount equal to the greater of (i) the Liquidation Value, plus all accumulated but unpaid Cash Distributions and Stock Dividends thereon to, but not including, the date of any liquidation, but excluding any Cash Premium and (ii) the amount that would be paid on such date in the event of a redemption following a change of control. On August 6, 2020, the Company declared a (i) cash distribution of $17.85 per share of Series A Preferred Stock, payable on October 15, 2020 , to holders of Series A Preferred Stock of record on the close of business on October 1, 2020 , and (ii) distributions payable in kind in a number of shares of Series A Preferred Stock as determined in accordance with the terms of the designation of the Series A Preferred Stock, payable on October 15, 2020 , to holders of Series A Preferred Stock of record on the close of business on October 1, 2020 . Series B Preferred Stock As of September 30, 2020, the Company had 3,750,000 shares of its Series B Preferred Stock authorized and 1,571,734 shares of Series B Preferred Stock outstanding. Series B Preferred Stock ranks senior to the Company’s common stock, with respect to distribution rights and rights upon liquidation, winding up and dissolution of the Company, and on parity with the Series A Preferred Stock and any other class or series of capital stock of the Company expressly designated as ranking on parity with the Series B Preferred Stock with respect to distribution rights and rights upon liquidation, winding up and dissolution of the Company, junior to any class or series of capital stock of the Company expressly designated as ranking senior to the Series B Preferred Stock with respect to distribution rights and rights upon liquidation, winding up and dissolution of the Company and junior in right of payment to the Company’s existing and future indebtedness. Holders of the Series B Preferred Stock generally do not have voting rights. Dividends on the Series B Preferred Stock are payable quarterly in arrears on the fifteenth (15th) day of January, April, July and October of each year (or if not a business day, on the immediately preceding business day) (each, a “dividend payment date”) at a rate equal to 7.00% of the $25.00 per share liquidation preference (equivalent to an annual rate of $1.7500 per share). On or after January 26, 2023, the Series B Preferred Stock may be redeemed, at the Company’s option, upon not less than 30 nor more than 60 days’ written notice, in whole or in part, at any time and from time to time, for cash at a redemption price equal to $25.00 per share, plus any accrued and unpaid dividends (whether or not authorized or declared) to, but excluding, the date fixed for redemption. Holders of Series B Preferred Stock will have no right to require the redemption or repurchase of the Series B Preferred Stock. Upon the occurrence of a Change of Control (as defined in the articles supplementary designating the terms of the Series B Preferred Stock (the “Series B Articles Supplementary”)), the Company may redeem for cash, in whole or in part, the Series B Preferred Stock within 120 days after the date on which such Change of Control occurred, by paying $25.00 per share, plus any accrued and unpaid dividends (whether or not authorized or declared) to, but excluding, the date fixed for redemption. In the event of any liquidation, dissolution or winding up of the Company, the holders of the Series B Preferred Stock shall be entitled to receive a liquidating distribution in the amount of  $25.00 per share, plus accrued and unpaid dividends (whether or not authorized or declared) to, but excluding, the date of final distribution to such holders. Series B Preferred Stock At-the-Market Offering Program On March 29, 2018, the Company and the Operating Company entered into a Distribution Agreement (the “Distribution Agreement”), by and among the Company, the Operating Company, the Manager and B. Riley FBR, Inc. (the “Agent”) in connection with the commencement of an at-the-market continuous offering program (the “Preferred ATM Program”). Pursuant to the terms and conditions of the Distribution Agreement, the Company may, from time to time, issue and sell through or to the Agent, shares of the Series B Preferred Stock, having an aggregate offering price of up to $45.0 million. As of September 30, 2020, the Company has sold 71,734 shares of Series B Preferred Stock at a weighted average price of $22.94, receiving net proceeds after commissions and other offering costs of $1.3 million under the Preferred ATM Program. The Preferred ATM Program was terminated upon the effectiveness of the Company’s registration statement on Form S-3 (File No. 333-231374) on July 12, 2019. ​ Non-controlling interests ​ Non-controlling interests are comprised of OC Units issued in connection with the acquisition of self-storage real estate owned (see Note 3, Self-Storage Investment Portfolio Significant Accounting Policies ). The Company reports these OC Units held by third parties as non-controlling interests. The Company records these non-controlling interests at their initial fair value, adjusting the basis prospectively for their share of the respective consolidated investments’ net income or loss and equity contributions and distributions. These non-controlling interests are not redeemable by the equity holders and are presented as part of permanent equity. Beginning on the first anniversary of the date of issuance, OC Units may be tendered for redemption by the holder thereof for cash per OC Unit equal to the then-current market price of the Company’s common stock, or at the Company’s option, shares of the Company’s common stock on a one-for-one basis based on the portion of the period the Units were outstanding. The income and losses attributed to non-controlling interests are also allocated based on the pro-rata weighted average Units outstanding.

EARNINGS PER SHARE

EARNINGS PER SHARE	9 Months Ended
	Sep. 30, 2020
EARNINGS PER SHARE [Abstract]
EARNINGS PER SHARE	10. EARNINGS PER SHARE Basic earnings per share is computed by dividing net income (loss) attributable to common shareholders by the weighted average number of shares outstanding during the period. Beginning on the first anniversary of the date of issuance, OC Units may be tendered for redemption by the holder thereof for cash per OC Unit equal to the then-current market price of the Company’s common stock, or at the Company’s option, shares of the Company’s common stock on a one-for-one basis and the income allocable to such OC Units is allocated on this same basis and reflected as non-controlling interests in the accompanying consolidated financial statements. All outstanding unvested restricted share awards that vest solely on a service condition contain rights to non-forfeitable dividends and participate in undistributed earnings with common shareholders and, accordingly, are considered participating securities that are included in the two-class method of computing basic earnings per share. Both the unvested restricted shares and the assumed share-settlement of the accrued stock dividend to holders of the Series A Preferred Stock, and the related impacts to earnings, are considered when calculating earnings per share on a diluted basis with the Company’s diluted earnings per share being the more dilutive of the treasury stock or two-class methods. Net losses are not attributed to participating securities and net loss attributable to common shareholders is adjusted for dividends declared on unvested restricted shares in periods with a net loss. Diluted earnings per share includes contingently issuable OC Units only if the market condition would have been met had the end of the reporting period been the measurement period. Stock awards with a market condition do not participate in nonforfeitable rights to dividends and are excluded from the calculation of diluted EPS. For the three and nine months ended September 30, 2020 and 2019, the Company’s basic earnings (loss) per share is computed using the two-class method, and the Company’s diluted earnings (loss) per share is computed using the more dilutive of the treasury stock method or two-class method: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 Shares outstanding ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares - basic ​ ​ 23,113,558 ​ ​ 22,019,875 ​ ​ 23,052,347 ​ ​ 21,173,946 Effect of dilutive securities (1) ​ ​ — ​ ​ 213,719 ​ ​ — ​ ​ 191,293 Weighted average common shares ​ ​ 23,113,558 ​ ​ 22,233,594 ​ ​ 23,052,347 ​ ​ 21,365,239 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Calculation of Earnings per Share - basic ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (5,631) ​ $ 10,954 ​ $ (61,407) ​ $ 37,941 Less: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income allocated to preferred stockholders ​ ​ 5,309 ​ ​ 5,157 ​ ​ 15,760 ​ ​ 15,283 Net loss attributable to non-controlling interest ​ ​ (1,005) ​ ​ — ​ ​ (3,604) ​ ​ — Net income allocated to unvested restricted shares (2) ​ ​ — ​ ​ 56 ​ ​ — ​ ​ 203 Dividends declared on unvested restricted shares ​ ​ — ​ ​ n/a ​ ​ 92 ​ ​ n/a Net income (loss) attributable to common shareholders, adjusted ​ $ (9,935) ​ $ 5,741 ​ $ (73,655) ​ $ 22,455 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares - basic ​ ​ 23,113,558 ​ ​ 22,019,875 ​ ​ 23,052,347 ​ ​ 21,173,946 Earnings (loss) per share - basic ​ $ (0.43) ​ $ 0.26 ​ $ (3.20) ​ $ 1.06 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Calculation of Earnings per Share - diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (5,631) ​ $ 10,954 ​ $ (61,407) ​ $ 37,941 Less: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income allocated to preferred stockholders ​ ​ 5,309 ​ ​ 5,157 ​ ​ 15,760 ​ ​ 15,283 Net loss attributable to non-controlling interest ​ ​ (1,005) ​ ​ — ​ ​ (3,604) ​ ​ — Dividends declared on unvested restricted shares ​ ​ — ​ ​ n/a ​ ​ 92 ​ ​ n/a Net income (loss) attributable to common shareholders, adjusted ​ $ (9,935) ​ $ 5,797 ​ $ (73,655) ​ $ 22,658 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares - diluted (1) ​ ​ 23,113,558 ​ ​ 22,233,594 ​ ​ 23,052,347 ​ ​ 21,365,239 Earnings (loss) per share - diluted ​ $ (0.43) ​ $ 0.26 ​ $ (3.20) ​ $ 1.06 ​ (1) Diluted earnings per share is calculated on the more dilutive of the treasury stock method or two-class method. For the three and nine months ended September 30, 2020, 2,354,407 OC Units and 1,699,478 OC Units respectively as well as their related losses were excluded from the calculation of diluted shares as they are not dilutive. 149,572 and 193,654 unvested restricted shares for the three and nine months ended September 30, 2020, respectively were also excluded as they are not dilutive. (2) Unvested restricted shares of common stock with vesting based on service participate in dividends with unrestricted shares of common stock on a 1:1 basis and thus are considered participating securities under the two-class method for the three and nine months ended September 30, 2020 and 2019. Under the two-class method, losses are not allocated to participating securities, therefore no loss was allocated to unvested restricted shares for the three and nine months ended September 30, 2020.

RELATED PARTY TRANSACTIONS

RELATED PARTY TRANSACTIONS	9 Months Ended
	Sep. 30, 2020
RELATED PARTY TRANSACTIONS [Abstract]
RELATED PARTY TRANSACTIONS	11. RELATED PARTY TRANSACTIONS Equity Method Investments Certain of the Company’s development property investments and bridge investments are equity method investments for which the Company has elected the fair value option of accounting. The fair value of these equity method investments at September 30, 2020 and December 31, 2019 was $316.3 million and $549.7 million, respectively. The interest income realized and the net unrealized loss from these equity method investments was net income of $9.5 million and $18.3 million for the three and nine months ended September 30, 2020 and the interest income and the net unrealized gain from these equity method investments was net income of $16.5 million and $47.2 million for the three and nine months ended September 30, 2019. ​ The Company’s investment in the real estate venture, the SL1 Venture, has a carrying amount of $4.1 million and $11.2 million at September 30, 2020 and December 31, 2019, respectively. The losses from this venture were $(2.0) million and $(2.2) million for the three and nine months ended September 30, 2020 and the earnings from this venture were $0.2 million and $0.4 million for the three and nine months ended September 30, 2019. ​ Management Agreement Prior to the completion of the Internalization, the Company relied on the personnel, properties and resources of the Manager to conduct its operations. The Company and the Manager were parties to a management agreement (as amended and restated, the “Management Agreement”), which was originally entered into on April 1, 2015 and was amended and restated on May 23, 2016, April 1, 2017 and November 1, 2017. Pursuant to the Management Agreement, the Manager was responsible for (a) the Company’s day-to-day operations (including finance, accounting and investor relations), (b) determining investment criteria and strategy in conjunction with the Company’s Board of Directors, (c) sourcing, analyzing, originating, underwriting, structuring, and acquiring the Company’s portfolio investments, (d) sourcing, analyzing, procuring and managing the Company’s capital and (e) performing portfolio management duties. The Manager has an Investment Committee that approves investments in accordance with the Company’s investment guidelines, investment strategy, and financing strategy. Management Fees Pursuant to the Management Agreement, the Company paid the Manager a base management fee in an amount equal to 0.375% of the Company’s stockholders’ equity (a 1.5% annual rate) calculated and payable quarterly in arrears in cash. For purposes of calculating the base management fee, the Company’s stockholder’s equity means: (a) the sum of (i) the net proceeds from all issuances of the Company’s equity securities since its IPO (allocated on a pro rata daily basis for such issuances during the fiscal quarter of any such issuance), plus (ii) the Company’s retained earnings at the end of the most recently completed fiscal quarter (without taking into account any non-cash equity compensation expense incurred in current or prior periods); less (b) any amount that the Company pays to repurchase its common stock since its IPO. If the Company’s retained earnings are in a net deficit position (following any required adjustments set forth below), then retained earnings shall not be included in stockholders’ equity. Retained earnings also excludes (x) any unrealized gains and losses and other non-cash items that have impacted stockholders’ equity as reported in the Company’s financial statements prepared in accordance with accounting principles generally accepted in the United States, or GAAP, and (y) one-time events pursuant to changes in GAAP (such as a cumulative change to the Company’s operating results as a result of a codification change pursuant to GAAP), and certain non-cash items not otherwise described above (such as depreciation and amortization), in each case after discussions between the Manager and the Company’s independent directors and approval by a majority of the Company’s independent directors. As a result, the Company’s stockholders’ equity, for purposes of calculating the base management fee, could be greater or less than the amount of stockholders’ equity shown on its financial statements. The base management fee is payable independent of the performance of the Company’s portfolio. The Manager computed the base management fee within 30 days after the end of the fiscal quarter with respect to which such installment is payable and promptly delivered such calculation to the Company’s Board of Directors. The amount of the installment shown in the calculation is due and payable no later than the date which is five business days after the date of delivery of such computation to the Board of Directors. The base management fee was $1.2 million, $2.1 million and $6.2 million for the period prior to Internalization ended February 20, 2020 and the three and nine months ended September 30, 2019, respectively. Incentive Fee The Manager was also able to earn an incentive fee each fiscal quarter (or part thereof that the Management Agreement is in effect) payable in arrears in cash. The incentive fee will be an amount, not less than zero, determined pursuant to the following formula: Incentive Fee = .20 times (A minus (B times .08)) minus C In the foregoing formula: ● A equals the Company’s Core Earnings (as defined below) for the previous 12-month period; ● B equals (i) the weighted average of the issue price per share of the Company’s common stock of all of its public offerings of common stock, multiplied by (ii) the weighted average number of all shares of common stock outstanding (including (i) any restricted stock units and any restricted shares of common stock in the previous 12-month period and (ii) shares of common stock issuable upon conversion of outstanding OC Units); and ● C equals the sum of any incentive fees earned by the Manager with respect to the first three fiscal quarters of such previous 12-month period. Notwithstanding application of the incentive fee formula, any incentive fee earned shall not be paid with respect to any fiscal quarter unless cumulative annual stockholder total return for the four most recently completed fiscal quarters is greater than 8%. Any computed incentive fee earned but not paid because of the foregoing hurdle will accrue until such 8% cumulative annual stockholder total return is achieved. The total return is calculated by adding stock price appreciation (based on the volume-weighted average of the closing price of the Company’s common stock on the New York Stock Exchange (or other applicable trading market) for the last ten consecutive trading days of the applicable computation period minus the volume-weighted average of the closing market price of the Company’s common stock for the last ten consecutive trading days of the period immediately preceding the applicable computation period) plus dividends per share paid during such computation period, divided by the volume-weighted average of the closing market price of the Company’s common stock for the last ten consecutive trading days of the period immediately preceding the applicable computation period. For purposes of computing the Incentive Fee, “Core Earnings” is defined as (1) net income (loss) determined under GAAP, plus (2) non-cash equity compensation expense, the incentive fee, depreciation and amortization, plus (3) any unrealized losses or other non-cash expense items reflected in GAAP net income (loss), less (4) any unrealized gains reflected in GAAP net income (including any unrealized appreciation with respect to self-storage facilities that the Company has not yet acquired). The amount was adjusted to exclude one-time events pursuant to changes in GAAP and certain other non-cash charges after discussions between the Manager and the Company’s independent directors and after approval by a majority of the independent directors. In addition, with respect to any self-storage facility acquired by the Company with respect to which it had an outstanding loan as of the time of such acquisition, the amount of Core Earnings determined pursuant to the formula above in the period of such acquisition shall also be increased by the difference between (A) the appraised value, as determined by a nationally recognized, independent third-party appraiser, mutually agreed to by the Company and the Manager, who has significant expertise in valuing self-storage properties, and (B) (i) the outstanding principal amount of any one of the Company’s loans secured by such acquired self-storage facility at the time of such acquisition plus (ii) any other consideration given to the former owner upon such acquisition. This addition is intended to include in Core Earnings the amount of the Company’s unrealized gain on account of its acquisition of a self-storage facility without such facility being sold to a third party buyer in the open market. The Manager computed the incentive fee each quarter within 45 days after the end of the fiscal quarter that is currently payable and if an incentive fee results, promptly delivers such calculation to the Company’s Board of Directors. The amount of any incentive fee shown in the calculation is due and payable no later than the date which is five business days after the date of delivery of such computation to the Board of Directors. The Manager did not earn an incentive fee for the period prior to Internalization ended February 20, 2020 and the three and nine months ended September 30, 2019. At September 30, 2020, the Company has no outstanding fees due to Manager. At December 31, 2019, the Company had outstanding fees due to Manager of $3.2 million consisting of the management fees payable, incentive fees payable, and certain reimbursable expenses. ​ Expense Reimbursement In addition to Management Fees and Incentive Fees as described above, the Management Agreement required that the Company reimburse payroll, occupancy, business development, marketing and other expenses of the Manager for conducting the business of the Company, excluding the salaries and cash bonuses of the Manager’s CEO and Chief Financial Officer (“CFO”), and certain other costs as determined by the Manager in accordance with the Management Agreement. Certain prepaid expenses and fixed assets are also purchased through the Manager and reimbursed by the Company. Under the Management Agreement, the Manager had the ability to engage independent contractors that provide investment banking, securities brokerage, mortgage brokerage and other financial, legal and account services as may be required for the Company’s investments, and the Company agreed to reimburse the Manager for costs and expenses incurred in connection with these services; however, expenses incurred by the Manager were reimbursable to the Manager by the Company only to the extent such expenses are not otherwise directly reimbursed by an unaffiliated third party. The amount of expenses to be reimbursed to the Manager by the Company are reduced dollar-for-dollar by the amount of any such payment or reimbursement. Amounts reimbursable to the Manager for expenses are included in general and administrative expenses in the Consolidated Statements of Operations and totaled $0.4 million, $1.1 million and $3.1 million for the period prior to Internalization ended February 20, 2020 and the three and nine months ended September 30, 2019, respectively.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	9 Months Ended
	Sep. 30, 2020
SUBSEQUENT EVENTS [Abstract]
SUBSEQUENT EVENTS	12. SUBSEQUENT EVENTS The Company’s management has evaluated subsequent events through the date of issuance of the consolidated financial statements included herein. Other than those disclosed below, there have been no subsequent events that occurred during such period that require disclosure or recognition in the accompanying consolidated financial statements. In October 2020, the Company acquired 100% of the Class A membership units of the LLCs that own the New York City 4, New York City 5 and Orlando 5 development property investments. With these acquisitions, the Company now wholly owns 43 facilities on its balance sheet or in its SL1 Joint Venture. ​ One of the four previously announced forgone investments, New York City 3, was repaid in full subsequent to September 30, 2020. ​ Delisting and Deregistration The Mergers, as previously described, were consummated on November 6, 2020. Also on November 6, 2020, The New York Stock Exchange filed a notification of removal from listing on Form 25 with the SEC with respect to the delisting and deregistration of the Company’s Common Stock. The Common Stock ceased being traded prior to the opening of the market on November 6, 2020, and is no longer listed on The New York Stock Exchange. Accordingly, the Company is no longer a publicly traded company. In addition, the Company intends to file with the SEC a Form 15 requesting the suspension of the reporting obligations of the Company under Sections 13(a) and 15(d) of the Securities Exchange Act of 1934, as amended. Debt Repayment and Termination On November 6, 2020, in connection with the Mergers, the Operating Company repaid all outstanding amounts owed under, and terminated, the Amended and Restated Credit Agreement with an aggregate outstanding amount of $242.6 million and the FirstBank Term Loans with an aggregate outstanding amount of $41.2 million. The Company did no t incur any material early termination penalties as a result of these terminations. The Company also terminated the interest rate swaps and interest rate caps related to the Amended and Restated Agreement resulting in a loss on termination of $1.1 million. Vesting of Restricted Stock and Payment of LTIP Payments On November 6, 2020, in connection with the Mergers, all previously unvested shares of restricted common stock of the Company vested fully, and employees of the Company who held such shares received the merger consideration in connection with the Mergers. The amount received in respect of previously unvested restricted common stock totaled $2.6 million. In addition, on November 6, 2020, in connection with the Mergers, a substantial majority of LTIP units granted to certain of the Company’s employees under its Long-Term Incentive Plan vested fully, and employees of the Company who held such LTIP units received an amount per vested LTIP unit equal to the merger consideration per share paid in connection with the Mergers. The amount received in respect of vesting of LTIP units totaled $1.0 million.

SIGNIFICANT ACCOUNTING POLICI_2

SIGNIFICANT ACCOUNTING POLICIES (Policies)	9 Months Ended
	Sep. 30, 2020
SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Basis of Presentation	Basis of Presentation ​ The Company’s consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States of America (“GAAP”). The accompanying interim consolidated financial statements include all normal recurring adjustments that are, in the opinion of management, necessary for a fair presentation of the results for the interim periods included therein. Substantially all operations are conducted through the Operating Company, and all significant intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates ​ The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect certain reported amounts and disclosures. Actual results could differ from those estimates. ​
Variable Interest Entities	Variable Interest Entities ​ The Company invests in entities that may qualify as variable interest entities (“VIEs”). A VIE is a legal entity that lacks one or more of the characteristics of a voting interest entity. A VIE is defined as an entity in which equity investors do not have the characteristics of a controlling financial interest or do not have sufficient equity at risk for the entity to finance its activities without additional subordinated financial support from other parties. The determination of whether an entity is a VIE includes both a qualitative and quantitative analysis. Management bases the qualitative analysis on its review of the design of the entity, its organizational structure including allocation of decision-making authority and relevant financial agreements and the quantitative analysis on the forecasted cash flow of the entity. Management reassesses the initial evaluation of an entity as a VIE upon the occurrence of certain reconsideration events. ​ A VIE must be consolidated only by its primary beneficiary, which is defined as the party that, along with its affiliates and agents, has both the: (i) power to direct the activities that most significantly impact the VIE’s economic performance and (ii) obligation to absorb the losses of the VIE or the right to receive the benefits from the VIE, which could be significant to the VIE. Management determines whether the Company is the primary beneficiary of a VIE by considering qualitative and quantitative factors, including, but not limited to: which activities most significantly impact the VIE’s economic performance and which party controls such activities; the amount and characteristics of its investment; the obligation or likelihood for the Company or other interests to provide financial support; and consideration of the VIE’s purpose and design, including the risks the VIE was designed to create and pass through to its variable interest holders and the similarity with and significance to the Company’s business activities and the other interests. Management reassesses the determination of whether the Company is the primary beneficiary of a VIE each reporting period. ​
Equity Investments	Equity Investments ​ Investments in real estate ventures and entities over which the Company exercises significant influence but not control are accounted for using the equity method. In accordance with Accounting Standards Codification (“ASC”) 825, Financial Instruments ​
Investments and Election of Fair Value Option of Accounting for Certain Investments	Investments and Election of Fair Value Option of Accounting for Certain Investments ​ The Company has elected the fair value option of accounting for all of its development property investments that are required under GAAP to be accounted for under the equity method, in order to provide stockholders and others who rely on the Company’s financial statements with a more complete and accurate understanding of the Company’s economic performance including its revenues and value inherent in the Company’s equity participation in development projects. Changes in the fair value of these investments are recorded in net unrealized gain (loss) on investments within other income. Interest income is reported in interest income from investments in the Consolidated Statements of Operations and is not included in the net unrealized gain on investments within other income. All direct loan costs are charged to expense as incurred. ​ Each loan investment, including those recorded at cost and presented on the Consolidated Balance Sheets as other loans, is evaluated for impairment on a periodic basis. For loans carried at fair value, indicators of impairment are reflected in the measurement of the loan. For loans that are carried at cost, the Company estimates an allowance for loan loss at each reporting date. In evaluating loan impairment, the Company also periodically evaluates the extent and impact of any credit deterioration associated with the performance and/or value of the underlying collateral property as well as the financial and operating capability of the borrower on a loan by loan basis. The Company also evaluates the financial wherewithal of any loan guarantors as well as the borrower’s competency in managing and operating the property, including the impact of the COVID-19 pandemic on property operations. In addition, the Company considers the overall economic environment, real estate sector and geographic sub-market in which the borrower operates. A loan will be considered impaired when, based on current information and events, it is probable that the loan will not be collected according to the contractual terms of the loan agreement. Factors to be considered by management in determining impairment include payment status, collateral value and the probability of collecting scheduled principal and interest payments when due. Loans that experience insignificant payment delays and payment shortfalls generally are not classified as impaired. ​
Realized Gains and Net Unrealized Gain (Loss) on Investments	Realized Gains and Net Unrealized Gain (Loss) on Investments ​ The Company measures realized gains by the difference between the net proceeds resulting from the sale of a self-storage property underlying one of the Company’s loan investments, excluding any prepayment penalties paid to the Company in connection with the repayment of the loan secured by the self-storage property, which are recognized in interest income from investments, and the cost basis of the investment, without regard to unrealized gain or loss previously recognized. “Net unrealized gain (loss) on investments” reflects the unrealized gains and losses recognized on certain investments during the reporting period, including any reversal of previously recorded unrealized gains when gains are realized. All fluctuations in fair value are included in net unrealized gain (loss) on investments on the Consolidated Statements of Operations.
Fair Value Measurement	Fair Value Measurement ​ The Company carries certain financial instruments at fair value because it has elected to apply the fair value option on an instrument by instrument basis under ASC 825-10. The Company’s financial instruments consist of cash, development property investments (which are generally structured as first mortgages and a 49.9% Profits Interest in the project), the investment in self-storage real estate venture, other loans, receivables, the secured revolving Credit Facility (as defined below), the term loans, payables, and derivative financial instruments. The following table presents the financial instruments measured at fair value on a recurring basis at September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Derivative financial instruments (asset position) ​ $ 47 ​ $ — ​ ​ 47 ​ ​ — Derivative financial instruments (liability position) ​ ​ (1,109) ​ ​ — ​ ​ (1,109) ​ ​ — Development property investments ​ ​ 316,254 ​ ​ — ​ ​ — ​ ​ 316,254 ​ The following table presents the financial instruments measured at fair value on a recurring basis at December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Derivative financial instruments (asset position) ​ $ 14 ​ $ — ​ $ 14 ​ $ — Derivative financial instruments (liability position) ​ ​ (393) ​ ​ — ​ ​ (393) ​ ​ — Development property investments ​ ​ 549,684 ​ ​ — ​ ​ — ​ ​ 549,684 ​ Estimating fair value requires the use of judgment. The types of judgments involved depend upon the availability of observable market information. Management’s judgments include determining the appropriate valuation model to use, estimating unobservable inputs and applying valuation adjustments. See Note 4, Fair Value of Financial Instruments ​
Derivative Instruments and Hedging Activities	Derivative Instruments and Hedging Activities ​ All derivative financial instruments are recorded on the balance sheet at fair value. Changes in fair value are recognized either in earnings or as other comprehensive income (loss), depending on whether the derivative has been designated as a fair value or cash flow hedge and whether it qualifies as part of a hedging relationship, the nature of the exposure being hedged, and how effective the derivative is at offsetting movements in underlying exposure. Hedge accounting is discontinued when it is determined that the derivative is no longer effective in offsetting changes in the fair value or cash flows of a hedged item; the derivative expires or is sold, terminated, or exercised; it is no longer probable that the forecasted transaction will occur; or management determines that designating the derivative as a hedging instrument is no longer appropriate. The Company uses interest rate swaps and interest rate caps to effectively convert a portion of its variable rate debt to fixed rate, thus reducing the impact of changes in interest rates on interest payments (see Note 7, Debt, Risk Management and Use of Financial Instruments ​ The changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in “Accumulated other comprehensive income (loss)” and is subsequently reclassified into earnings in the period that the hedged forecasted transaction affects earnings. In accordance with ASU 2017-12, Derivatives and Hedging (Topic 815) as long as a hedging instrument is designated and the results of the effectiveness testing support that the instrument qualifies for hedge accounting treatment, there is no longer the requirement for periodic measurement or recognition of ineffectiveness. Rather, the full impact of hedge gains and losses will be recognized in the period in which hedged transactions impact earnings, regardless of whether or not economic mismatches exist in the hedging relationship. Amounts reported in “Accumulated other comprehensive income (loss)” related to derivatives designated as qualifying cash flow hedges will be reclassified to interest expense as interest payments are made on the Company's variable rate or fixed rate debt. Changes in fair value for financial instruments not designated as cash flow hedges are recognized in earnings within interest expense in the Consolidated Statements of Operations.
Self-Storage Real Estate Owned	Self-Storage Real Estate Owned ​ To date, all self-storage real estate owned has consisted of self-storage facilities that were developed and constructed with financing provided by the Company. Each facility collateralized a mortgage loan that, together with the related Profits Interest, was reported by the Company as a development property investment carried at fair value. Each such property became self-storage real estate owned during the period when the Company acquired the developer’s interest in the entity that owns the facility. After such time, fair value accounting for such investment ceases. ​ Land is carried at historical cost. Building and improvements are carried at historical cost less accumulated depreciation and impairment losses. The cost consists primarily of: (i) the funded principal balance of the loan to the Company, net of unamortized origination fees; (ii) unrealized appreciation recognized as of the acquisition date; and (iii) the cash consideration paid and assumed liabilities, if applicable, to acquire the interests of other equity owners of the project. Ordinary repairs and maintenance are expensed as incurred; major replacements and betterments, which improve or extend the life of the asset, are capitalized and depreciated over their estimated useful lives. The costs of building and improvements are generally depreciated using the straight-line method based on a useful life of 40 years. ​ All of the Company’s acquisitions have been asset acquisitions and the Company expects that the majority of future self-storage facility acquisitions will be considered asset acquisitions, however, the Company will continue to evaluate each future acquisition using Accounting Standards Update (“ASU”) 2017-01 - Business Combinations (Topic 805): Clarifying the Definition of a Business to determine whether accounting for a business combination or asset acquisition applies. When facilities are acquired, the cost is allocated to the tangible and intangible assets acquired and liabilities assumed based on relative fair values. Allocations to the individual assets and liabilities are based upon their relative fair values as estimated by management. ​ In allocating the purchase price for an acquisition, the Company determines whether the acquisition includes intangible assets or liabilities. The Company allocates a portion of the cost to an intangible asset attributable to the value of in-place leases. This intangible asset is amortized to expense over the expected remaining term of the respective leases, which is generally one year. Substantially all the leases in place at acquired facilities are at market rates, as the majority of the leases are month-to-month contracts. Accordingly, to date, no portion of the basis for an acquired property has been allocated to above- or below-market lease intangibles. To date, no intangible asset has been recorded for the value of customer relationships, because the Company does not have any concentrations of significant customers and the average customer turnover is frequent. ​ The Company evaluates long-lived assets for impairment when events and circumstances, such as declines in occupancy and operating results, indicate that there may be an impairment. The carrying value of these long-lived assets is compared to the undiscounted future net operating cash flows, plus a terminal value, attributable to the assets to determine if the facility’s basis is recoverable. If an asset’s basis is not considered recoverable, an impairment loss is recorded to the extent the net carrying value of the asset exceeds the fair value. The impairment loss recognized equals the excess of net carrying value over the related fair value of the asset. There were no impairment losses recognized in accordance with these procedures during the three or nine months ended September 30, 2020 or during the year ended December 31, 2019. ​
Cash and Cash Equivalents	Cash and Cash Equivalents ​ Cash, investments in money market accounts and certificates of deposit with original maturities of three months or less are considered to be cash equivalents. The Company places its cash and cash equivalents primarily with three financial institutions, and the balance at two of the financial institutions exceeds the Federal Deposit Insurance Corporation insurance limit. ​
Other Loans	Other Loans ​ The Company’s other loans balance primarily includes principal balances for certain revolving loan agreements, short-term mortgage loans, and land loans made by the Company in situations where it was determined that making such loans would benefit the Company’s primary business. These loans are accounted for under the cost method, and fair value approximates cost at September 30, 2020 and December 31, 2019. None of these loans are in non-accrual status as of September 30, 2020 and December 31, 2019. The Company determined that no allowance for loan loss was necessary at September 30, 2020 and December 31, 2019. ​
Fixed Assets	Fixed Assets ​ Fixed assets are recorded at cost and consist of furniture, office and computer equipment, and software. Depreciation is computed on a straight-line basis over the estimated useful lives of the related assets, which range from three
Goodwill	Goodwill ​ Goodwill represents the excess of consideration paid over the fair value of underlying identifiable net assets of businesses acquired. During the nine months ended September 30, 2020, the Company recorded $4.7 million of Goodwill related to the Internalization, and the Company has one reporting unit. Goodwill has an indeterminate life and is not amortized, but is tested for impairment on an annual basis, or more frequently if events or changes in circumstances indicate that the asset might be impaired. Subsequent to the Internalization, the Company determined that dramatically deteriorating macroeconomic conditions driven by the impact of the COVID-19 pandemic on capital markets, and specifically the Company’s market capitalization, was a triggering event for an interim goodwill impairment test. In accordance with ASC 350, Intangibles - Goodwill and Other , since the Company’s common stock is traded in an active market, the Company calculated its fair value primarily based on the Company’s market capitalization as of March 31, 2020. The fair value calculated as of March 31, 2020, was determined to be below the Company’s carrying value. As a result, the Company recorded a goodwill impairment loss of $4.7 million for the nine months ended September 30, 2020, and there is no Goodwill as of September 30, 2020 or December 31, 2019.
Revenue Recognition	Revenue Recognition ​ Interest income is recognized as earned on a simple interest basis and is reported in interest income from investments in the Consolidated Statements of Operations. Accrual of interest will be discontinued on a loan when management believes, after considering economic and business conditions and collection efforts, that the borrower’s financial condition is such that collection of interest is doubtful. The Company will recognize income on impaired loans when they are placed into non-accrual status on a cash basis when the loans are both current and the collateral on the loan is sufficient to cover the outstanding obligation to the Company. If these factors do not exist, the Company will not recognize income on such loans. ​ The Company’s loan origination fees are accreted into interest income over the term of the investment using the effective yield method. ​ The operations of the self-storage real estate owned are managed by a third-party self-storage management company. All rental leases are operating leases, and rental income is recognized in accordance with the terms of the leases, which generally are month to month.
Debt Issuance Costs	Debt Issuance Costs ​ Costs related to the issuance of a debt instrument are deferred and amortized as interest expense over the estimated life of the related debt instrument using the straight-line method, which approximates the effective interest method. If a debt instrument is repurchased, modified, or exchanged prior to its original maturity date, the Company evaluates both the unamortized balance of debt issuance costs as well as any new debt issuance costs, including third party fees, to determine if the costs should be written off to interest expense or, if significant, included in “loss on modification or extinguishment of debt” in the Consolidated Statements of Operations. Debt issuance costs related to the term loans are presented in the Consolidated Balance Sheets as a deduction from the carrying amount of the principal balance. Debt issuance costs related to the revolving Credit Facility are presented in the Consolidated Balance Sheets as Deferred Financing Costs.
Internalization Expenses	Internalization Expenses As described in Note 1, Organization and Formation ​ ​ ​ ​ ​ OC Units issuable as Initial Consideration (1) : $ 33,538 ​ OC Units contingently issuable as Earn Out Consideration (2) : ​ 8,554 ​ ​ $ 42,092 ​ (1) Represents the fair value of 1,794,872 OC Units issuable as the Initial Consideration based upon the Company's closing stock price as of February 20, 2020 of $20.31 adjusted for an 8% marketability discount for the fair value impact of the one year holding period and annual limits on selling of OC Units. (2) Represents the fair value of 769,231 OC Units issuable as the Earn Out Consideration contingent upon (1) the Company’s common stock trading at or above a daily volume weighted price of $25.00 per share for at least 30 days during any trailing 365-day period prior to December 31, 2024, or (2) a change of control of the Company that is approved by the board of directors and stockholders of the Company occurring prior to December 31, 2024, based on a Black-Scholes Merton valuation of the OC Units. The significant assumptions utilized in the valuation of the Earn Out Consideration were a risk-free rate of 1.41% , a dividend yield of 4.53% , volatility of 27% , and a marketability discount of 8% . ​ In accordance with ASC 805, Business Combinations excess consideration paid over the fair value of underlying identifiable net assets of businesses acquired was recorded as Goodwill. The table below presents the revenue and net income of the business combination on a pro forma basis as if the Internalization occurred on January 1, 2019. As the Manager’s historical revenues were entirely comprised of amounts received from the Company for management services performed by the Manager and intercompany amounts are eliminated in consolidation, there was no pro forma adjustment to the Company’s revenue for the nine months ended September 30, 2020 and 2019. Pro forma net loss for the nine months ended September 30, 2020 includes the elimination of non-recurring expenses for the settlement of the pre-existing contractual agreement of $37.4 million and acquisition related expenses of $0.4 million. Pro forma adjustments for the periods ended September 30, 2020 and 2019, also include the impact of additional compensation expense for employees previously employed by the Manager and the elimination of fees paid to the Manager. The pro forma results are not necessarily indicative of the results which actually would have occurred if the business combination had occurred on the first day of the periods presented, nor does the pro forma financial information purport to represent the results of operations for future periods. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ Nine Months Ended September 30, 2019 Pro forma total revenue (unaudited) $ 35,242 ​ ​ ​ $ 32,965 ​ Pro forma net income (loss) allocable to common shares (unaudited) ​ (35,236) ​ ​ ​ ​ 25,882 ​
Offering and Registration Costs	Offering and Registration Costs ​ Offering and registration costs represent underwriting discounts and commissions, professional fees, fees paid to various regulatory agencies, and other costs incurred in connection with the registration and sale of the Company’s securities. Offering and registration costs incurred in connection with the Company’s stock offerings are reflected as a reduction of additional paid-in capital.
Income Taxes	Income Taxes ​ The Company has elected to be taxed as a REIT and to comply with the related provisions of the Code. Accordingly, the Company will generally not be subject to U.S. federal income tax to the extent of its distributions to stockholders and as long as certain asset, income and share ownership tests are met. To qualify as a REIT, the Company must annually distribute at least 90% of its REIT taxable income to its stockholders and meet certain other requirements. ​
Earnings per Share ("EPS")	Earnings per Share (“EPS”) ​ Basic EPS includes only the weighted average number of common shares outstanding during the period. Diluted EPS includes the weighted average number of common shares and the dilutive effect of restricted stock, accrued stock dividends, and redeemable OC Units when such instruments are dilutive. ​ All outstanding unvested share-based payment awards that contain rights to nonforfeitable dividends are treated as participating in undistributed earnings with common shareholders. Awards of this nature are considered participating securities and the two-class method of computing basic and diluted EPS must be applied. Beginning on the first anniversary of the date of issuance, OC Units may be tendered for redemption by the holder thereof for cash per OC Unit equal to the then-current market price of the Company’s common stock, or at the Company’s option, shares of the Company’s common stock on a one-for-one basis and the income allocable to such OC Units is allocated on this same basis and reflected as non-controlling interests in the accompanying consolidated financial statements. The Company’s diluted earnings per share represents the more dilutive of the treasury stock or two-class methods and OC Units are included in dilutive earnings per share calculations when the units are dilutive to earnings per share. Net losses are not attributed to participating securities and net loss attributable to common shareholders is adjusted for dividends declared on unvested restricted shares in periods with a net loss. Diluted earnings per share includes contingently issuable OC Units only if the market condition would have been met had the end of the reporting period been the measurement period. Stock awards with a market condition do not participate in nonforfeitable rights to dividends and are excluded from the calculation of diluted EPS.
Segment Reporting	Segment Reporting ​ The Company does not evaluate performance on a relationship specific or transactional basis and does not distinguish its principal business or group its operations on a geographical basis for purposes of measuring performance. Accordingly, the Company believes it has a single ​
Recent Accounting Pronouncements	Recent Accounting Pronouncements ​ In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. This ASU significantly changes how entities will measure credit losses for most financial assets and certain other instruments that are not measured at fair value through net income. This guidance is effective for smaller reporting companies for fiscal years and for interim periods within those fiscal years, beginning after December 15, 2022, with early adoption being allowed as of the fiscal years beginning after December 15, 2018. The Company is currently assessing the impact this new accounting guidance will have on its consolidated financial statements; however, the Company does not expect the new accounting guidance to have a material impact on its consolidated financial statements. ​ In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848). This ASU contains practical expedients for reference rate reform related activities that impact debt, leases, derivatives and other contracts. The guidance in this ASU is optional and may be elected over time as reference rate reform activities occur. For the three and nine months ended September 30, 2020, the Company has elected to apply the hedge accounting expedients related to probability and the assessments of effectiveness for future LIBOR-indexed cash flows to assume that the index upon which future hedged transactions will be based matches the index on the corresponding derivatives. Application of these expedients preserves the presentation of derivatives consistent with past presentation. The Company continues to evaluate the impact of the guidance and may apply other elections as applicable as additional changes in the market occur.

SIGNIFICANT ACCOUNTING POLICI_3

SIGNIFICANT ACCOUNTING POLICIES (Tables)	9 Months Ended
	Sep. 30, 2020
SIGNIFICANT ACCOUNTING POLICIES [Abstract]
Financial Instruments Measured at Fair Value on a Recurring Basis	The following table presents the financial instruments measured at fair value on a recurring basis at September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Derivative financial instruments (asset position) ​ $ 47 ​ $ — ​ ​ 47 ​ ​ — Derivative financial instruments (liability position) ​ ​ (1,109) ​ ​ — ​ ​ (1,109) ​ ​ — Development property investments ​ ​ 316,254 ​ ​ — ​ ​ — ​ ​ 316,254 ​ The following table presents the financial instruments measured at fair value on a recurring basis at December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Fair Value Measurements Using ​ ​ Total ​ Level 1 ​ Level 2 ​ Level 3 Derivative financial instruments (asset position) ​ $ 14 ​ $ — ​ $ 14 ​ $ — Derivative financial instruments (liability position) ​ ​ (393) ​ ​ — ​ ​ (393) ​ ​ — Development property investments ​ ​ 549,684 ​ ​ — ​ ​ — ​ ​ 549,684
Consideration for the Internalization Transaction	As described in Note 1, Organization and Formation ​ ​ ​ ​ ​ OC Units issuable as Initial Consideration (1) : $ 33,538 ​ OC Units contingently issuable as Earn Out Consideration (2) : ​ 8,554 ​ ​ $ 42,092 ​ (1) Represents the fair value of 1,794,872 OC Units issuable as the Initial Consideration based upon the Company's closing stock price as of February 20, 2020 of $20.31 adjusted for an 8% marketability discount for the fair value impact of the one year holding period and annual limits on selling of OC Units. (2) Represents the fair value of 769,231 OC Units issuable as the Earn Out Consideration contingent upon (1) the Company’s common stock trading at or above a daily volume weighted price of $25.00 per share for at least 30 days during any trailing 365-day period prior to December 31, 2024, or (2) a change of control of the Company that is approved by the board of directors and stockholders of the Company occurring prior to December 31, 2024, based on a Black-Scholes Merton valuation of the OC Units. The significant assumptions utilized in the valuation of the Earn Out Consideration were a risk-free rate of 1.41% , a dividend yield of 4.53% , volatility of 27% , and a marketability discount of 8% .
Internalization, Proforma Information	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine Months Ended September 30, 2020 ​ ​ Nine Months Ended September 30, 2019 Pro forma total revenue (unaudited) $ 35,242 ​ ​ ​ $ 32,965 ​ Pro forma net income (loss) allocable to common shares (unaudited) ​ (35,236) ​ ​ ​ ​ 25,882 ​
Consolidated Statements of Cash Flows - Supplemental Disclosures	The following table provides supplemental disclosures related to the Consolidated Statements of Cash Flows: ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, ​ ​ 2020 ​ 2019 Supplemental disclosure of cash flow information: ​ ​ ​ ​ ​ ​ Interest paid ​ $ 6,986 ​ $ 3,359 ​ ​ ​ ​ ​ ​ ​ Supplemental disclosure of non-cash investing and financing activities: ​ ​ ​ ​ ​ ​ Stock dividend paid on preferred stock ​ $ 6,375 ​ $ 6,375 Dividends declared, but not paid, on preferred stock ​ ​ 5,309 ​ ​ 5,157 Dividends declared, but not paid, on common stock ​ ​ — ​ ​ 7,783 Dividends declared, but not paid, on OC Units ​ ​ — ​ ​ — Reclassification of development property investments to self-storage real estate owned ​ ​ 255,495 ​ ​ 125,715 Reclassification of other assets and liabilities to self-storage real estate owned ​ ​ 1,074 ​ ​ — Other loans paid off with issuance of development property investments ​ ​ — ​ ​ 404 OC Units issued for self-storage real estate owned acquisitions ​ ​ 7,978 ​ ​ — OC Units issued for Internalization ​ ​ 33,538 ​ ​ — Contingent consideration for Internalization ​ ​ 8,554 ​ ​ —

SELF-STORAGE INVESTMENT PORTF_2

SELF-STORAGE INVESTMENT PORTFOLIO (Tables)	9 Months Ended
	Sep. 30, 2020
SELF-STORAGE INVESTMENT PORTFOLIO [Abstract]
Schedule of Investments	As of September 30, 2020, the aggregate committed principal amount of the Company’s development property investments was approximately $314.5 million and outstanding principal was $283.3 million, as described in more detail in the table below (dollars in thousands): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Metropolitan ​ Total ​ ​ ​ ​ Remaining ​ ​ ​ ​ ​ Statistical Area ​ Investment ​ Funded ​ Unfunded ​ ​ ​ Closing Date ​ ("MSA") ​ Commitment ​ Investment (1) ​ Commitment ​ Fair Value Development property investments (includes a profits interest): ​ ​ ​ ​ ​ ​ ​ ​ ​ 7/2/2015 ​ Milwaukee (2)(7) ​ $ 7,650 ​ $ 7,648 ​ $ 2 ​ $ 8,316 10/27/2015 ​ Austin (2)(7) ​ ​ 8,658 ​ ​ 8,184 ​ ​ 474 ​ ​ 8,071 2/24/2017 ​ New Orleans (2)(7) ​ ​ 12,549 ​ ​ 12,371 ​ ​ 178 ​ ​ 15,017 3/1/2017 ​ Houston (2)(9) ​ ​ 14,825 ​ ​ 14,825 ​ ​ — ​ ​ 15,661 5/2/2017 ​ Tampa 2 (2)(7) ​ ​ 8,091 ​ ​ 7,984 ​ ​ 107 ​ ​ 9,444 5/19/2017 ​ Tampa 3 (2)(7) ​ ​ 9,224 ​ ​ 8,618 ​ ​ 606 ​ ​ 10,561 6/12/2017 ​ Tampa 4 (2)(7) ​ ​ 10,266 ​ ​ 10,014 ​ ​ 252 ​ ​ 13,317 6/29/2017 ​ Boston 1 (2)(6) ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,850 8/30/2017 ​ Orlando 4 (2)(7) ​ ​ 9,037 ​ ​ 8,329 ​ ​ 708 ​ ​ 10,376 9/14/2017 ​ Los Angeles 1 ​ ​ 28,750 ​ ​ 10,923 ​ ​ 17,827 ​ ​ 11,143 9/14/2017 ​ Miami 1 (3) ​ ​ 14,657 ​ ​ 14,463 ​ ​ 194 ​ ​ 15,657 10/12/2017 ​ Miami 2 (4)(10) ​ ​ — ​ ​ 1,661 ​ ​ — ​ ​ 1,459 10/30/2017 ​ New York City 3 (4)(10) ​ ​ — ​ ​ 8,261 ​ ​ — ​ ​ 7,916 11/16/2017 ​ Miami 3 (2)(4)(7) ​ ​ 20,168 ​ ​ 19,093 ​ ​ 1,745 ​ ​ 21,914 12/15/2017 ​ New York City 4 (2)(7) ​ ​ 10,591 ​ ​ 9,747 ​ ​ 844 ​ ​ 11,435 12/28/2017 ​ New York City 5 (2) ​ ​ 16,073 ​ ​ 16,064 ​ ​ 9 ​ ​ 17,646 3/30/2018 ​ Philadelphia (2)(4)(8) ​ ​ 14,338 ​ ​ 11,536 ​ ​ 3,264 ​ ​ 11,313 5/1/2018 ​ Miami 9 (4)(10) ​ ​ — ​ ​ 3,877 ​ ​ — ​ ​ 3,639 5/15/2018 ​ Atlanta 7 (2)(7) ​ ​ 9,418 ​ ​ 8,502 ​ ​ 916 ​ ​ 9,948 5/23/2018 ​ Kansas City (2)(7) ​ ​ 9,968 ​ ​ 8,754 ​ ​ 1,214 ​ ​ 10,489 6/7/2018 ​ Orlando 5 (2) ​ ​ 12,969 ​ ​ 12,057 ​ ​ 912 ​ ​ 13,885 11/16/2018 ​ Baltimore 2 (10) ​ ​ — ​ ​ 785 ​ ​ — ​ ​ 690 3/1/2019 ​ New York City 6 ​ ​ 18,796 ​ ​ 4,297 ​ ​ 14,499 ​ ​ 4,311 4/18/2019 ​ New York City 7 (3)(4) ​ ​ 23,462 ​ ​ 15,781 ​ ​ 8,050 ​ ​ 17,374 ​ ​ ​ ​ $ 259,490 ​ $ 223,774 ​ $ 51,801 ​ $ 253,432 Preferred equity investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 6/12/2018 ​ Los Angeles 2 (3)(5) ​ ​ 9,298 ​ ​ 9,659 ​ ​ 649 ​ ​ 10,384 3/15/2019 ​ Stamford (2)(5) ​ ​ 2,904 ​ ​ 3,222 ​ ​ — ​ ​ 5,479 5/8/2019 ​ New York City 8 (5) ​ ​ 21,000 ​ ​ 23,073 ​ ​ — ​ ​ 23,492 7/11/2019 ​ New York City 9 (5) ​ ​ 13,095 ​ ​ 14,218 ​ ​ — ​ ​ 14,177 8/21/2019 ​ New York City 10 (5) ​ ​ 8,674 ​ ​ 9,346 ​ ​ — ​ ​ 9,290 ​ ​ ​ ​ $ 54,971 ​ $ 59,518 ​ $ 649 ​ $ 62,822 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investments reported at fair value ​ $ 314,461 ​ $ 283,292 ​ $ 52,450 ​ $ 316,254 ​ (1) (2) Fair Value of Financial Instruments (3) Fair Value of Financial Instruments (4) (5) (6) (7) (8) (9) (10) The Company has re-assessed these development property investments for which either development or construction has not yet commenced and communicated our intent to forgo those projects with the respective developers. The Company and its respective developer partners on these investments are in active dialogues concerning the repayment of its outstanding principal along with any current and future accrued interest. As of December 31, 2019, the aggregate committed principal amount of the Company’s development property investments was approximately $608.9 million and outstanding principal was $478.6 million, as described in more detail in the table below (dollars in thousands) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Metropolitan ​ Total ​ ​ ​ ​ Remaining ​ ​ ​ ​ ​ Statistical Area ​ Investment ​ Funded ​ Unfunded ​ ​ ​ Closing Date ​ ("MSA") ​ Commitment ​ Investment (1) ​ Commitment ​ Fair Value Development property investments (includes a profits interest): ​ ​ ​ ​ ​ ​ ​ ​ ​ 7/2/2015 ​ Milwaukee (2)(7) ​ $ 7,650 ​ $ 7,648 ​ $ 2 ​ $ 8,884 8/14/2015 ​ Raleigh (2)(7)(10) ​ ​ 8,792 ​ ​ 8,789 ​ ​ 3 ​ ​ 8,593 10/27/2015 ​ Austin (2)(7) ​ ​ 8,658 ​ ​ 8,136 ​ ​ 522 ​ ​ 8,099 9/20/2016 ​ Charlotte 2 (2)(7)(10) ​ ​ 12,888 ​ ​ 12,677 ​ ​ 211 ​ ​ 13,984 1/18/2017 ​ Atlanta 3 (2)(7)(10) ​ ​ 14,115 ​ ​ 13,297 ​ ​ 818 ​ ​ 16,130 1/31/2017 ​ Atlanta 4 (2)(7)(10) ​ ​ 13,678 ​ ​ 13,497 ​ ​ 181 ​ ​ 17,082 2/24/2017 ​ Orlando 3 (2)(7)(10) ​ ​ 8,056 ​ ​ 7,767 ​ ​ 289 ​ ​ 9,725 2/24/2017 ​ New Orleans (2)(7) ​ ​ 12,549 ​ ​ 12,021 ​ ​ 528 ​ ​ 14,504 2/27/2017 ​ Atlanta 5 (2)(7)(10) ​ ​ 17,492 ​ ​ 17,492 ​ ​ — ​ ​ 19,970 3/1/2017 ​ Fort Lauderdale (2)(7)(10) ​ ​ 9,952 ​ ​ 9,383 ​ ​ 569 ​ ​ 13,635 3/1/2017 ​ Houston (2)(9) ​ ​ 14,825 ​ ​ 14,825 ​ ​ — ​ ​ 17,820 4/14/2017 ​ Louisville 1 (2)(7)(10) ​ ​ 8,523 ​ ​ 7,552 ​ ​ 971 ​ ​ 9,550 4/20/2017 ​ Denver 1 (2)(7)(10) ​ ​ 9,806 ​ ​ 9,616 ​ ​ 190 ​ ​ 10,947 4/20/2017 ​ Denver 2 (2)(7) ​ ​ 11,164 ​ ​ 11,009 ​ ​ 155 ​ ​ 12,383 5/2/2017 ​ Atlanta 6 (2)(7)(10) ​ ​ 12,543 ​ ​ 12,025 ​ ​ 518 ​ ​ 14,744 5/2/2017 ​ Tampa 2 (2)(7) ​ ​ 8,091 ​ ​ 7,644 ​ ​ 447 ​ ​ 9,196 5/19/2017 ​ Tampa 3 (2)(7) ​ ​ 9,224 ​ ​ 8,326 ​ ​ 898 ​ ​ 10,086 6/12/2017 ​ Tampa 4 (2)(7) ​ ​ 10,266 ​ ​ 9,614 ​ ​ 652 ​ ​ 12,673 6/19/2017 ​ Baltimore 1 (2)(4)(7)(10) ​ ​ 10,775 ​ ​ 11,010 ​ ​ 274 ​ ​ 13,581 6/28/2017 ​ Knoxville (2)(7)(10) ​ ​ 9,115 ​ ​ 8,628 ​ ​ 487 ​ ​ 10,355 6/29/2017 ​ Boston 1 (2)(6) ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,361 6/30/2017 ​ New York City 2 (2)(4)(10) ​ ​ 27,982 ​ ​ 28,974 ​ ​ 665 ​ ​ 31,047 7/27/2017 ​ Jacksonville 3 (2)(7)(10) ​ ​ 8,096 ​ ​ 7,751 ​ ​ 345 ​ ​ 10,129 8/30/2017 ​ Orlando 4 (2)(7) ​ ​ 9,037 ​ ​ 8,107 ​ ​ 930 ​ ​ 10,251 9/14/2017 ​ Los Angeles 1 ​ ​ 28,750 ​ ​ 10,157 ​ ​ 18,593 ​ ​ 10,347 9/14/2017 ​ Miami 1 (3) ​ ​ 14,657 ​ ​ 12,618 ​ ​ 2,039 ​ ​ 13,373 9/28/2017 ​ Louisville 2 (2)(7)(10) ​ ​ 9,940 ​ ​ 9,530 ​ ​ 410 ​ ​ 11,688 10/12/2017 ​ Miami 2 (4) ​ ​ 9,459 ​ ​ 1,494 ​ ​ 8,045 ​ ​ 1,280 10/30/2017 ​ New York City 3 (4) ​ ​ 15,301 ​ ​ 6,776 ​ ​ 8,822 ​ ​ 6,383 11/16/2017 ​ Miami 3 (3)(4) ​ ​ 20,168 ​ ​ 12,086 ​ ​ 8,413 ​ ​ 12,898 11/21/2017 ​ Minneapolis 1 (2)(7)(10) ​ ​ 12,674 ​ ​ 10,684 ​ ​ 1,990 ​ ​ 12,290 12/1/2017 ​ Boston 2 (2)(7)(10) ​ ​ 8,771 ​ ​ 7,918 ​ ​ 853 ​ ​ 10,024 12/15/2017 ​ New York City 4 (3) ​ ​ 10,591 ​ ​ 6,705 ​ ​ 3,886 ​ ​ 7,528 12/27/2017 ​ Boston 3 ​ ​ 10,174 ​ ​ 2,757 ​ ​ 7,417 ​ ​ 2,674 12/28/2017 ​ New York City 5 (2) ​ ​ 16,073 ​ ​ 13,817 ​ ​ 2,256 ​ ​ 16,373 2/8/2018 ​ Minneapolis 2 (2)(7)(10)) ​ ​ 10,543 ​ ​ 9,904 ​ ​ 639 ​ ​ 11,763 3/30/2018 ​ Philadelphia (2)(4)(8) ​ ​ 14,338 ​ ​ 11,536 ​ ​ 3,263 ​ ​ 11,807 4/6/2018 ​ Minneapolis 3 (2)(7)(10) ​ ​ 12,883 ​ ​ 10,337 ​ ​ 2,546 ​ ​ 12,043 5/1/2018 ​ Miami 9 (4) ​ ​ 12,421 ​ ​ 3,560 ​ ​ 9,006 ​ ​ 3,427 5/15/2018 ​ Atlanta 7 (3) ​ ​ 9,418 ​ ​ 6,563 ​ ​ 2,855 ​ ​ 7,683 5/23/2018 ​ Kansas City (2) ​ ​ 9,968 ​ ​ 8,235 ​ ​ 1,733 ​ ​ 9,663 6/7/2018 ​ Orlando 5 (2) ​ ​ 12,969 ​ ​ 10,340 ​ ​ 2,629 ​ ​ 11,780 11/16/2018 ​ Baltimore 2 ​ ​ 9,247 ​ ​ 757 ​ ​ 8,490 ​ ​ 709 3/1/2019 ​ New York City 6 ​ ​ 18,796 ​ ​ 3,168 ​ ​ 15,628 ​ ​ 3,122 4/18/2019 ​ New York City 7 (4) ​ ​ 23,462 ​ ​ 7,304 ​ ​ 16,287 ​ ​ 7,067 ​ ​ ​ ​ $ 553,880 ​ $ 422,034 ​ $ 135,455 ​ $ 490,651 Preferred equity investments: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 6/12/2018 ​ Los Angeles 2 (5) ​ ​ 9,298 ​ ​ 9,173 ​ ​ 649 ​ ​ 9,403 3/15/2019 ​ Stamford (2)(5) ​ ​ 2,904 ​ ​ 3,064 ​ ​ — ​ ​ 4,952 5/8/2019 ​ New York City 8 (5) ​ ​ 21,000 ​ ​ 21,945 ​ ​ — ​ ​ 22,359 7/11/2019 ​ New York City 9 (5) ​ ​ 13,095 ​ ​ 13,526 ​ ​ — ​ ​ 13,489 8/21/2019 ​ New York City 10 (5) ​ ​ 8,674 ​ ​ 8,892 ​ ​ — ​ ​ 8,830 ​ ​ ​ ​ $ 54,971 ​ $ 56,600 ​ $ 649 ​ $ 59,033 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Total investments reported at fair value ​ $ 608,851 ​ $ 478,634 ​ $ 136,104 ​ $ 549,684 (1) (2) Fair Value of Financial Instruments (3) Fair Value of Financial Instruments (4) (5) (6) (7) (8) (9) (10) During the nine months ended September 30, 2020, the Company purchased its partner’s 50.1% Profits Interest in this investment.
Schedule of Changes in Fair Value of Investments	The following table provides a reconciliation of the funded principal to the fair market value of investments at September 30, 2020: ​ ​ ​ ​ ​ ​ ​ ​ Funded principal $ 283,292 Adjustments: ​ ​ ​ Unamortized origination and other fees ​ ​ (3,292) Net unrealized gain (loss) on investments ​ ​ 36,340 Other ​ ​ (86) Fair value of investments ​ $ 316,254 The following table provides a reconciliation of the funded principal to the fair market value of investments at December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ Funded principal $ 478,634 Adjustments: ​ ​ ​ Unamortized origination and other fees ​ ​ (5,633) Net unrealized gain (loss) on investments ​ ​ 76,767 Other ​ ​ (84) Fair value of investments ​ $ 549,684
Real Estate Investment, Impact in Consolidated Balance Sheet , Disclosure	​ The following table shows the components of the real estate investments as presented in the Company’s accompanying Consolidated Balance Sheets as of September 30, 2020 and December 31, 2019: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ December 31, 2019 Land ​ $ 72,262 ​ $ 29,430 Building and improvements ​ ​ 448,796 ​ ​ 186,295 In-place leases ​ ​ 16,128 ​ ​ 8,629 Property equipment ​ ​ 217 ​ ​ 122 Construction-in-progress ​ ​ — ​ ​ 16,460 Accumulated depreciation and amortization ​ ​ (23,410) ​ ​ (10,092) Self-storage real estate owned, net ​ $ 513,993 ​ $ 230,844

FAIR VALUE OF FINANCIAL INSTR_2

FAIR VALUE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
Summary of Valuation Techniques and Inputs Used to Measure the Fair Value	The following table summarizes the instruments measured at fair value on a recurring basis categorized in Level 3 of the fair value hierarchy and the valuation techniques and inputs used to measure their fair value. ​ ​ ​ ​ ​ ​ Instrument ​ Valuation technique and assumptions ​ Hierarchy classification ​ ​ ​ ​ ​ Development property investments with a profits interest ​ Valuations are determined using an Income Approach analysis, using the discounted cash flow method model, capturing the prepayment penalty / call price schedule as applicable. The valuation models are calibrated to the total investment net drawn amount as of the issuance date factoring in the value of the Profits Interests. Typically, the calibration is done on an investment level basis. In certain instances, the Company may acquire a portfolio of investments in which case the calibration is done on an aggregate basis to the aggregate net drawn amount as of the date of issuance. ​ Level 3
Schedule of Change in Fair Value of Investments Due to Change in Market Yield Discount Rates	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Increase (decrease) in fair value of investments Change in market yields/discount rates (in millions) ​ September 30, 2020 ​ December 31, 2019 Up 25 basis points ​ $ (1.1) ​ $ (2.1) Down 25 basis points, subject to a minimum yield/rate of 10 basis points ​ ​ 0.5 ​ ​ 2.2 ​ ​ ​ ​ ​ ​ ​ Up 50 basis points ​ ​ (2.2) ​ ​ (4.2) Down 50 basis points, subject to a minimum yield/rate of 10 basis points ​ ​ 0.5 ​ ​ 4.5
Schedule Of Change In Fair Value of Investments Due to Change in Capitalization Rates	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Increase (decrease) in fair value of investments Change in capitalization rates (in millions) ​ September 30, 2020 ​ December 31, 2019 Up 25 basis points ​ $ (4.8) ​ $ (10.2) Down 25 basis points ​ ​ 5.2 ​ ​ 11.1 ​ ​ ​ ​ ​ ​ ​ Up 50 basis points ​ ​ (9.5) ​ ​ (19.4) Down 50 basis points ​ ​ 11.0 ​ ​ 23.4
Changes in Investments that Use Level 3 Inputs	The following tables present changes in investments that use Level 3 inputs: ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2019 $ 549,684 Realized gains ​ ​ — Unrealized losses ​ ​ (5,630) Fundings of principal and change in unamortized origination fees ​ ​ 26,354 Repayments of loans ​ ​ (13,878) Payment-in-kind interest ​ ​ 15,219 Reclassification of self-storage real estate owned ​ ​ (255,495) Net transfers in or out of Level 3 ​ ​ — Balance at September 30, 2020 ​ $ 316,254 ​ ​ ​ ​ ​ ​ ​ ​ ​ Balance at December 31, 2018 ​ $ 457,947 Unrealized gains ​ ​ 28,847 Fundings of principal and change in unamortized origination fees ​ ​ 126,100 Repayments of loans ​ ​ (361) Payment-in-kind interest ​ ​ 22,069 Reclassification of self-storage real estate owned ​ ​ (125,715) Net transfers in or out of Level 3 ​ ​ — Balance at September 30, 2019 ​ $ 508,887
Fair Value, Inputs, Level 3 [Member]
Summary of Valuation Techniques and Inputs Used to Measure the Fair Value	The following tables summarize the significant unobservable inputs the Company used to value its investments categorized within Level 3 as of September 30, 2020 and December 31, 2019. These tables are not intended to be all-inclusive, but instead to capture the significant unobservable inputs relevant to the Company’s determination of fair values. The significant unobservable inputs associated with the Philadelphia and Houston investments are not included as the fair value was determined based on the fair value of the underlying collateral. The fair value of the underlying collateral was determined, in part, by using a market comparable approach and an income approach based on a capitalization rate within the range provided below for capitalization rates associated with development property investments with a profits interest. ​ ​ ​ ​ ​ ​ ​ ​ As of September 30, 2020 ​ ​ Unobservable Inputs Primary Valuation ​ ​ ​ ​ ​ Weighted Techniques ​ Input ​ Estimated Range ​ Average Income approach analysis ​ Market yields/discount rate ​ 6.94 - 9.16% ​ 8.10% ​ ​ Exit date (a) ​ 0.83 - 5.94 years ​ 3.65 years ​ ​ ​ ​ ​ ​ ​ Option pricing model ​ Volatility ​ 67.03 - 96.75% ​ 78.51% ​ ​ Exit date (a) ​ 0.83 - 5.94 years ​ 3.65 years ​ ​ Capitalization rate (b) ​ 5.25 - 5.50% ​ 5.43% ​ ​ Discount rate (b) ​ 8.25 - 8.50% ​ 8.43% (a) The exit dates for the development property investments are generally the estimated date of stabilization of the underlying property. (b) Twenty properties were 40% - 100% complete, thus requiring a capitalization rate and/or discount rate to derive entrepreneurial profit, which are used to derive the enterprise value input to the OPM. Capitalization rates are estimated based on current data derived from independent sources in the markets in which the Company holds investments. ​ ​ ​ ​ ​ ​ ​ As of December 31, 2019 ​ ​ Unobservable Inputs Primary Valuation ​ ​ ​ ​ ​ Weighted Techniques ​ Input ​ Estimated Range ​ Average Income approach analysis ​ Market yields/discount rate ​ 6.89 - 10.16% ​ 8.39% ​ ​ Exit date (a) ​ 1.50 - 6.69 years ​ 3.40 years ​ ​ ​ ​ ​ ​ ​ Option pricing model ​ Volatility ​ 60.95 - 93.83% ​ 73.24% ​ ​ Exit date (a) ​ 1.50 - 6.69 years ​ 3.40 years ​ ​ Capitalization rate (b) ​ 4.75 - 5.75% ​ 5.46% ​ ​ Discount rate (b) ​ 7.75 - 8.75% ​ 8.46% (a) The exit dates for the development property investments are generally the estimated date of stabilization of the underlying property. (b) Thirty-eight properties were 40% - 100% complete, thus requiring a capitalization rate and/or discount rate to derive entrepreneurial profit, which are used to derive the enterprise value input to the OPM. Capitalization rates are estimated based on current data derived from independent sources in the markets in which the Company holds investments.

INVESTMENT IN SELF-STORAGE RE_2

INVESTMENT IN SELF-STORAGE REAL ESTATE VENTURE (Tables)	9 Months Ended
	Sep. 30, 2020
INVESTMENT IN SELF-STORAGE REAL ESTATE VENTURE [Abstract]
Equity Method Investments	The SL1 Venture has elected the fair value option of accounting for its development property investments with a Profits Interest, which are equity method investments of the SL1 Venture. The assumptions used to value the SL1 Venture’s investments are materially consistent with those used to value the Company’s investments. As of September 30, 2020, the SL1 Venture had five development property investments with a Profits Interest as described in more detail in the table below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Metropolitan ​ ​ ​ ​ ​ ​ ​ Remaining ​ ​ ​ ​ ​ Statistical Area ​ Total Investment ​ Funded ​ Unfunded ​ ​ ​ Closing Date ​ ("MSA") ​ Commitment ​ Investment (1) ​ Commitment ​ Fair Value 5/14/2015 ​ Miami 1 (2)(3)(4) ​ $ — ​ $ — ​ $ — ​ $ 1,638 5/14/2015 ​ Miami 2 (2)(3)(4) ​ ​ — ​ ​ — ​ ​ — ​ ​ 1,702 9/25/2015 ​ Fort Lauderdale (2)(3)(4) ​ ​ — ​ ​ — ​ ​ — ​ ​ 4,211 4/15/2016 ​ Washington DC (3)(4) ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,727 7/21/2016 ​ New Jersey (3) ​ ​ 7,828 ​ ​ 7,471 ​ ​ 357 ​ ​ 8,880 ​ ​ Total ​ $ 7,828 ​ $ 7,471 ​ $ 357 ​ $ 20,158 ​ ​ (1) Represents principal balance of loan gross of origination fees. The principal balance includes interest accrued on the investment. (2) These development property investments (having approximately $8.1 million of outstanding principal at contribution) were contributed to the SL1 Venture on March 31, 2016 by the Company. (3) Certificate of occupancy had been received as of September 30, 2020. See Note 4, Fair Value of Financial Instruments , for information regarding recognition of entrepreneurial profit. (4) The SL1 Venture’s loan was repaid in full through a refinancing initiated by the SL1 Venture’s partner. This investment represents the SL1 Venture’s 49.9% Profits Interest which was retained during the transaction. ​ As of December 31, 2019, the SL1 Venture had six development property investments with a Profits Interest as described in more detail in the table below: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Metropolitan ​ ​ ​ ​ ​ ​ ​ Remaining ​ ​ ​ ​ ​ Statistical Area ​ Total Investment ​ Funded ​ Unfunded ​ ​ ​ Closing Date ​ ("MSA") ​ Commitment ​ Investment (1) ​ Commitment ​ Fair Value 5/14/2015 ​ Miami 1 (2)(3) ​ $ 13,867 ​ $ 13,114 ​ $ 753 ​ $ 16,222 5/14/2015 ​ Miami 2 (2)(3) ​ ​ 14,849 ​ ​ 14,519 ​ ​ 330 ​ ​ 16,588 9/25/2015 ​ Fort Lauderdale (2)(3) ​ ​ 13,230 ​ ​ 12,899 ​ ​ 331 ​ ​ 17,156 4/15/2016 ​ Washington DC (3)(4) ​ ​ — ​ ​ — ​ ​ — ​ ​ 3,339 7/21/2016 ​ New Jersey (3) ​ ​ 7,828 ​ ​ 7,357 ​ ​ 471 ​ ​ 9,036 9/28/2016 ​ Columbia (3) ​ ​ 9,199 ​ ​ 9,073 ​ ​ 126 ​ ​ 10,445 ​ ​ Total ​ $ 58,973 ​ $ 56,962 ​ $ 2,011 ​ $ 72,786 (1) Represents principal balance of loan gross of origination fees. The principal balance includes interest accrued on the investment. (2) These development property investments (having approximately $8.1 million of outstanding principal at contribution) were contributed to the SL1 Venture on March 31, 2016 by the Company. (3) Certificate of occupancy had been received as of December 31, 2019. See Note 4, Fair Value of Financial Instruments , for information regarding recognition of entrepreneurial profit. (4) The SL1 Venture’s loan was repaid in full through a refinancing initiated by the SL1 Venture’s partner. This investment represents the SL1 Venture’s 49.9% Profits Interest which was retained during the transaction.

VARIABLE INTEREST ENTITIES (Tab

VARIABLE INTEREST ENTITIES (Tables)	9 Months Ended
	Sep. 30, 2020
VARIABLE INTEREST ENTITIES [Abstract]
Schedule of Variable Interest Entities	The Company has recorded assets of $316.3 million and $549.7 million at September 30, 2020 and December 31, 2019, respectively, for its variable interest in the development property investment VIEs which is included in the development property investments at fair value line items in the Consolidated Balance Sheets. The Company’s maximum exposure to loss as a result of its involvement with the development property investment VIEs is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ September 30, 2020 ​ December 31, 2019 Assets recorded related to VIEs ​ $ 316,254 ​ $ 549,684 Unfunded loan commitments to VIEs ​ ​ 52,450 ​ ​ 136,104 Maximum exposure to loss ​ $ 368,704 ​ $ 685,788

DEBT (Tables)

DEBT (Tables)	9 Months Ended
	Sep. 30, 2020
DEBT [Abstract]
Schedule of debt	A summary of the Company’s debt is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Effective ​ Carrying Value as of ​ Maturity Date ​ Interest Rate ​ September 30, 2020 ​ December 31, 2019 Secured revolving credit facility (1) March 24, 2023 ​ 2.65% ​ $ 242,000 ​ $ 162,000 Term Loans: ​ ​ ​ ​ ​ ​ ​ ​ ​ Term loan 1 (2) August 1, 2021 ​ 2.41% ​ ​ 9,150 ​ ​ 9,150 Term loan 2 (2) August 1, 2021 ​ 2.41% ​ ​ 7,125 ​ ​ 7,125 Term loan 3 (2) August 1, 2021 ​ 2.41% ​ ​ 8,625 ​ ​ 8,625 Term loan 4 (2) August 1, 2021 ​ 2.41% ​ ​ 9,188 ​ ​ 9,188 Term loan 5 (2) August 1, 2021 ​ 2.41% ​ ​ 7,087 ​ ​ 7,087 Total Term Loans ​ ​ ​ ​ ​ 41,175 ​ ​ 41,175 Term loan debt issuance costs ​ ​ ​ ​ ​ (202) ​ ​ (384) Net Term Loans ​ ​ ​ ​ ​ 40,973 ​ ​ 40,791 Total debt ​ ​ ​ ​ $ 282,973 ​ $ 202,791 (1) Risk Management and Use of Financial Instruments (2) Risk Management and Use of Financial Instruments

RISK MANAGEMENT AND USE OF FI_2

RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS (Tables)	9 Months Ended
	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Schedule of changes in accumulated other comprehensive loss	The changes in accumulated other comprehensive income (loss) for the three and nine months ended September 30, 2020 and 2019, are summarized as follows ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ Nine months ended ​ ​ September 30, ​ September 30, ​ ​ ​ 2020 ​ ​ 2019 ​ ​ 2020 ​ ​ 2019 Accumulated other comprehensive income beginning of period ​ $ (1,268) ​ $ (441) ​ $ (393) ​ $ — Other comprehensive income (loss): ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Unrealized gains (losses) on interest rate swaps ​ ​ (54) ​ ​ (58) ​ ​ (1,152) ​ ​ (495) Reclassification of realized losses (gains) on interest rate swaps ​ ​ 238 ​ ​ (1) ​ ​ 461 ​ ​ (5) Amount included in other comprehensive income (loss) ​ ​ 184 ​ ​ (59) ​ ​ (691) ​ ​ (500) Accumulated other comprehensive income (loss) end of period ​ $ (1,084) ​ $ (500) ​ $ (1,084) ​ $ (500)
Designated [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Schedule of terms and fair values of derivative financial instruments designated as hedges	The following table summarizes the terms and fair values of the Company’s derivative financial instruments designated as hedges as of September 30, 2020 and December 31, 2019, respectively ( dollars in thousands ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Notional Amount ​ ​ ​ ​ ​ ​ ​ Fair Value Hedge Product Hedge Type (1) ​ September 30, 2020 December 31, 2019 Strike ​ Effective Date ​ Maturity ​ September 30, 2020 December 31, 2019 Swap ​ Cash flow ​ $ 9,150 ​ $ 9,150 ​ 2.2925% ​ 6/3/2019 ​ 8/1/2021 ​ $ (165) ​ $ (104) Swap ​ Cash flow ​ ​ 7,125 ​ ​ 7,125 ​ 2.2925% ​ 6/3/2019 ​ 8/1/2021 ​ ​ (129) ​ ​ (81) Swap ​ Cash flow ​ ​ 8,625 ​ ​ 8,625 ​ 2.2925% ​ 6/3/2019 ​ 8/1/2021 ​ ​ (155) ​ ​ (98) Swap ​ Cash flow ​ ​ 9,188 ​ ​ 9,188 ​ 2.2925% ​ 6/3/2019 ​ 8/1/2021 ​ ​ (165) ​ ​ (105) Swap ​ Cash flow ​ ​ 7,087 ​ ​ 7,087 ​ 1.6025% ​ 8/13/2019 ​ 8/1/2021 ​ ​ (87) ​ ​ (5) Swap ​ Cash flow ​ ​ 100,000 ​ ​ — ​ 0.3570% ​ 5/1/2020 ​ 3/24/2023 ​ ​ (408) ​ ​ — ​ ​ ​ ​ $ 141,175 ​ $ 41,175 ​ ​ ​ ​ ​ ​ ​ $ (1,109) ​ $ (393) (1) ​
Schedule of effect of derivatives gain loss on the consolidated statements of comprehensive income	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives in Cash Flow Hedging Relationships ​ Amount of Gain (Loss) Recognized in Accumulated OCL on Derivative ​ Loss Reclassified from Accumulated OCL into Interest Expense (Income) ​ Location of Loss Reclassified from Accumulated OCL into Expense (Income) Three months ended September 30, ​ 2020 ​ 2019 ​ 2020 ​ 2019 ​ ​ ​ ​ ​ ​ Term loan interest rate contracts ​ $ (54) ​ $ (58) ​ $ 238 ​ $ (1) ​ Interest Expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Term loan interest rate contracts ​ $ (1,152) ​ $ (495) ​ $ 461 ​ $ (5) ​ Interest Expense
Nondesignated [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Schedule of effect of derivatives gain loss on the consolidated statements of comprehensive income	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Derivatives Not Designated as Hedging Instruments ​ Amount of Gain (Loss) Recognized in Earnings on Derivative ​ ​ Location of Gain (Loss) Recognized in Income on Derivative Three months ended September 30, ​ 2020 ​ 2019 ​ ​ ​ ​ ​ ​ Credit Facility interest rate cap ​ $ (127) ​ $ (61) ​ ​ Interest Expense ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended September 30, ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Credit Facility interest rate cap ​ $ (208) ​ $ (89) ​ ​ Interest Expense

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	9 Months Ended
	Sep. 30, 2020
Restricted Stock [Member]
Summary of Changes in Restricted Shares	A summary of changes in the Company’s restricted shares of common stock for the three and nine months ended September 30, 2020 and 2019 is as follows: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ Three months ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ ​ average grant ​ ​ ​ average grant ​ ​ Shares ​ date fair value ​ Shares ​ date fair value Unvested at June 30, ​ ​ 150,836 ​ $ 20.93 ​ ​ 208,665 ​ $ 20.35 Granted ​ ​ — ​ ​ - ​ ​ 7,500 ​ ​ 19.84 Vested ​ ​ (1,875) ​ ​ 19.84 ​ ​ — ​ ​ - Forfeited ​ ​ — ​ ​ — ​ ​ — ​ ​ - Unvested at September 30, ​ ​ 148,961 ​ $ 20.94 ​ ​ 216,165 ​ $ 20.34 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended ​ Nine months ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ ​ average grant ​ ​ ​ average grant ​ ​ Shares ​ date fair value ​ Shares ​ date fair value Unvested at December 31, ​ ​ 216,165 ​ $ 20.34 ​ ​ 159,165 ​ $ 18.39 Granted ​ ​ 59,402 ​ ​ 18.00 ​ ​ 145,922 ​ ​ 21.60 Vested ​ ​ (126,606) ​ ​ 18.53 ​ ​ (87,256) ​ ​ 18.95 Forfeited ​ ​ — ​ ​ — ​ ​ (1,666) ​ ​ 18.10 Unvested at September 30, ​ ​ 148,961 ​ $ 20.94 ​ ​ 216,165 ​ $ 20.34
Restricted Stock Units (RSUs) [Member]
Summary of Changes in Restricted Shares	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended ​ Three months ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ ​ average grant ​ ​ ​ average grant ​ ​ RSUs ​ date fair value ​ RSUs ​ date fair value Unvested at June 30, ​ ​ 31,243 ​ $ 26.00 ​ ​ — ​ $ — Granted ​ ​ — ​ ​ — ​ ​ — ​ ​ — Unvested at September 30, ​ ​ 31,243 ​ $ 26.00 ​ ​ — ​ $ — ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Nine months ended ​ Nine months ended ​ ​ September 30, 2020 ​ September 30, 2019 ​ ​ ​ ​ ​ Weighted ​ ​ ​ Weighted ​ ​ ​ ​ ​ average grant ​ ​ ​ average grant ​ ​ Shares ​ date fair value ​ Shares ​ date fair value Unvested at December 31, ​ ​ — ​ $ — ​ ​ — ​ $ — Granted ​ ​ 31,243 ​ ​ 26.00 ​ ​ — ​ ​ — Unvested at September 30, ​ ​ 31,243 ​ $ 26.00 ​ ​ — ​ $ —

EARNINGS PER SHARE (Tables)

EARNINGS PER SHARE (Tables)	9 Months Ended
	Sep. 30, 2020
EARNINGS PER SHARE [Abstract]
Schedule of Earnings per Share, Basic and Diluted	​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Three months ended September 30, ​ Nine months ended September 30, ​ ​ 2020 ​ 2019 ​ 2020 ​ 2019 Shares outstanding ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares - basic ​ ​ 23,113,558 ​ ​ 22,019,875 ​ ​ 23,052,347 ​ ​ 21,173,946 Effect of dilutive securities (1) ​ ​ — ​ ​ 213,719 ​ ​ — ​ ​ 191,293 Weighted average common shares ​ ​ 23,113,558 ​ ​ 22,233,594 ​ ​ 23,052,347 ​ ​ 21,365,239 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Calculation of Earnings per Share - basic ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (5,631) ​ $ 10,954 ​ $ (61,407) ​ $ 37,941 Less: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income allocated to preferred stockholders ​ ​ 5,309 ​ ​ 5,157 ​ ​ 15,760 ​ ​ 15,283 Net loss attributable to non-controlling interest ​ ​ (1,005) ​ ​ — ​ ​ (3,604) ​ ​ — Net income allocated to unvested restricted shares (2) ​ ​ — ​ ​ 56 ​ ​ — ​ ​ 203 Dividends declared on unvested restricted shares ​ ​ — ​ ​ n/a ​ ​ 92 ​ ​ n/a Net income (loss) attributable to common shareholders, adjusted ​ $ (9,935) ​ $ 5,741 ​ $ (73,655) ​ $ 22,455 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares - basic ​ ​ 23,113,558 ​ ​ 22,019,875 ​ ​ 23,052,347 ​ ​ 21,173,946 Earnings (loss) per share - basic ​ $ (0.43) ​ $ 0.26 ​ $ (3.20) ​ $ 1.06 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Calculation of Earnings per Share - diluted ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income (loss) ​ $ (5,631) ​ $ 10,954 ​ $ (61,407) ​ $ 37,941 Less: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Net income allocated to preferred stockholders ​ ​ 5,309 ​ ​ 5,157 ​ ​ 15,760 ​ ​ 15,283 Net loss attributable to non-controlling interest ​ ​ (1,005) ​ ​ — ​ ​ (3,604) ​ ​ — Dividends declared on unvested restricted shares ​ ​ — ​ ​ n/a ​ ​ 92 ​ ​ n/a Net income (loss) attributable to common shareholders, adjusted ​ $ (9,935) ​ $ 5,797 ​ $ (73,655) ​ $ 22,658 ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Weighted average common shares - diluted (1) ​ ​ 23,113,558 ​ ​ 22,233,594 ​ ​ 23,052,347 ​ ​ 21,365,239 Earnings (loss) per share - diluted ​ $ (0.43) ​ $ 0.26 ​ $ (3.20) ​ $ 1.06 ​ (1) Diluted earnings per share is calculated on the more dilutive of the treasury stock method or two-class method. For the three and nine months ended September 30, 2020, 2,354,407 OC Units and 1,699,478 OC Units respectively as well as their related losses were excluded from the calculation of diluted shares as they are not dilutive. 149,572 and 193,654 unvested restricted shares for the three and nine months ended September 30, 2020, respectively were also excluded as they are not dilutive. (2) Unvested restricted shares of common stock with vesting based on service participate in dividends with unrestricted shares of common stock on a 1:1 basis and thus are considered participating securities under the two-class method for the three and nine months ended September 30, 2020 and 2019. Under the two-class method, losses are not allocated to participating securities, therefore no loss was allocated to unvested restricted shares for the three and nine months ended September 30, 2020.

ORGANIZATION AND FORMATION OF_2

ORGANIZATION AND FORMATION OF THE COMPANY (Narrative) (Details)	Feb. 20, 2020$ / sharesshares	Sep. 30, 2020$ / sharesshares	Dec. 31, 2019$ / sharesshares	Nov. 06, 2020$ / sharesshares	Jul. 27, 2016$ / shares
Operations commenced date		Oct. 1, 2014
Initial public offering		initial public offering (the “IPO”) on April 1, 2015.
Common stock, par value (in dollars per share) | $ / shares		$ 0.01	$ 0.01
Common stock, shares outstanding		23,263,130	22,423,283
Operating Company Units [Member] | Initial Consideration [Member] | Operating Company [Member]
Operating Company Units issuable for Internalization, shares	1,794,872
Operating Company Units [Member] | Earn Out Consideration [Member] | Operating Company [Member]
Operating Company Units issuable for Internalization, shares	769,231
Share Price [Member] | Operating Company Units [Member] | Initial Consideration [Member] | Operating Company [Member]
Internalization, Measurement input | $ / shares	20.31
Share Price [Member] | Operating Company Units [Member] | Earn Out Consideration [Member] | Operating Company [Member]
Internalization, Measurement input | $ / shares	25
Series A Preferred Stock [Member]
Preferred stock, shares outstanding		139,875	133,500
Preferred stock, dividend rate		7.00%	7.00%
Preferred stock, liquidation preference per share | $ / shares					$ 1,000
Series B Preferred Stock [Member]
Preferred stock, shares outstanding		1,571,734	1,571,734
Preferred stock, dividend rate		7.00%	7.00%
Preferred stock, liquidation preference per share | $ / shares		$ 25
Subsequent Event [Member] | Operating Company [Member]
Common stock, shares outstanding				0
Subsequent Event [Member] | NexPoint RE Merger, Inc. [Member]
Common stock, shares outstanding				0
Subsequent Event [Member] | Common Stock Class [Member] | NexPoint RE Merger, Inc. [Member]
Merger agreement, price per share | $ / shares				$ 17.30
Subsequent Event [Member] | Series A Preferred Stock [Member] | NexPoint RE Merger, Inc. [Member]
Preferred stock, shares outstanding				0
Subsequent Event [Member] | Series B Preferred Stock [Member] | NexPoint RE Merger, Inc. [Member]
Preferred stock, shares outstanding				0

SIGNIFICANT ACCOUNTING POLICI_4

SIGNIFICANT ACCOUNTING POLICIES (Narrative) (Details) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)segment	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)	Feb. 20, 2020USD ($)
Significant Accounting Policies [Line Items]
Number of reporting units | segment			1
Finite-lived intangible asset, useful life			1 year
Self-Storage Real Estate Owned, impairment loss	$ 0		$ 0		$ 0
Allowance for loan loss	0		0		0
Goodwill	4,700		4,700		$ 0	$ 4,700
Goodwill impairment loss	0	$ 0	4,738	$ 0
Internalization - settlement of preexisting contractual relationship			$ 37,353	$ 0
Number of operating segments | segment			1
Acquisition-related expenses recognized in other expenses	0		$ 400
Leases, Acquired-above-or Below-Market [Member]
Significant Accounting Policies [Line Items]
Intangible assets	0		0
Customer Relationships [Member]
Significant Accounting Policies [Line Items]
Intangible assets	$ 0		$ 0
Assets Leased to Others [Member]
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life			40 years
Property, plant and equipment, depreciation methods			straight-line method
Furniture, Office, Computer Equipment and Software [Member]
Significant Accounting Policies [Line Items]
Property, plant and equipment, depreciation methods			straight-line basis
Development Property and Bridge Loan Investments [Member]
Significant Accounting Policies [Line Items]
Equity method investment, ownership percentage	49.90%		49.90%
Maximum [Member] | Furniture, Office, Computer Equipment and Software [Member]
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life			7 years
Minimum [Member] | Furniture, Office, Computer Equipment and Software [Member]
Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life			3 years
Operating Company [Member] | Operating Company Units [Member]
Significant Accounting Policies [Line Items]
Total amount of consideration for the Internalization						$ 42,092

SIGNIFICANT ACCOUNTING POLICI_5

SIGNIFICANT ACCOUNTING POLICIES (Financial Instruments Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments (asset position)	$ 47	$ 14
Derivative financial instruments (liability position)	(1,109)	(393)
Development property investments at fair value	316,254	549,684
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments (asset position)	0	0
Derivative financial instruments (liability position)	0	0
Development property investments at fair value	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments (asset position)	47	14
Derivative financial instruments (liability position)	(1,109)	(393)
Development property investments at fair value	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative financial instruments (asset position)	0	0
Derivative financial instruments (liability position)	0	0
Development property investments at fair value	$ 316,254	$ 549,684

SIGNIFICANT ACCOUNTING POLICI_6

SIGNIFICANT ACCOUNTING POLICIES (Consideration for the Internalization) (Details) - Operating Company [Member] - Operating Company Units [Member]	Feb. 20, 2020USD ($)$ / sharesshares
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Total amount of consideration for the Internalization	$ 42,092,000
Initial Consideration [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Operating Company Units issuable as Initial Consideration	$ 33,538,000
Operating Company Units issuable for Internalization, shares | shares	1,794,872
Initial Consideration [Member] | Share Price [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Internalization, Measurement input | $ / shares	20.31
Initial Consideration [Member] | Marketability Discount [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Internalization, Measurement input	0.08
Earn Out Consideration [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Operating Company Units issuable for Internalization	$ 8,554,000
Operating Company Units issuable for Internalization, shares | shares	769,231
Earn Out Consideration [Member] | Share Price [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Internalization, Measurement input | $ / shares	25
Earn Out Consideration [Member] | Risk Free Interest Rate [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Internalization, Measurement input	0.0141
Earn Out Consideration [Member] | Dividend Yield [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Internalization, Measurement input	0.0453
Earn Out Consideration [Member] | Volatility [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Internalization, Measurement input	0.27
Earn Out Consideration [Member] | Marketability Discount [Member]
Business Acquisition, Equity Interests Issued or Issuable [Line Items]
Internalization, Measurement input	0.08

SIGNIFICANT ACCOUNTING POLICI_7

SIGNIFICANT ACCOUNTING POLICIES (Internalization, Pro Forma Information) (Details) - Operating Company [Member] - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Pro forma total revenue	$ 35,242	$ 32,965
Pro forma net income (loss) allocable to common shares	$ (35,236)	$ 25,882

SIGNIFICANT ACCOUNTING POLICI_8

SIGNIFICANT ACCOUNTING POLICIES (Schedule of Consolidated Statements of Cash Flows - Supplemental Disclosures) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Supplemental disclosure of cash flow information:
Interest paid							$ 6,986	$ 3,359
Supplemental disclosure of non-cash investing and financing activities:
Stock dividend paid on preferred stock	$ 2,125	$ 2,125	$ 2,125	$ 2,125	$ 2,125	$ 2,125	6,375	6,375
Dividends declared, but not paid, on preferred stock							5,309	5,157
Dividends declared, but not paid, on common stock							0	7,783
Dividends declared, but not paid, on OC Units							0	0
Reclassification of development property investments to self-storage real estate owned							255,495	125,715
Reclassification of other assets and liabilities to self-storage real estate owned							1,074	0
Other loans paid off with issuance of development property investments							0	404
Contingent consideration for Internalization							8,554	0
Property Acquisition [Member]
Supplemental disclosure of non-cash investing and financing activities:
OC Units issued for Internalization	1,285	5,157	1,536
Internalization Expenses [Member]
Supplemental disclosure of non-cash investing and financing activities:
OC Units issued for Internalization			42,092
Non-Controlling Interests [Member] | Property Acquisition [Member]
Supplemental disclosure of non-cash investing and financing activities:
OC Units issued for self-storage real estate owned acquisitions							7,978	0
OC Units issued for Internalization	$ 1,285	$ 5,157	1,536
Non-Controlling Interests [Member] | Internalization Expenses [Member]
Supplemental disclosure of non-cash investing and financing activities:
OC Units issued for Internalization			$ 33,538				$ 33,538	$ 0

SELF-STORAGE REAL ESTATE OWNED

SELF-STORAGE REAL ESTATE OWNED (Narrative) (Details) $ in Thousands	Sep. 30, 2020USD ($)property	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)property	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)	Jul. 31, 2020	Jul. 15, 2020	Jun. 30, 2020	May 06, 2020	Apr. 10, 2020	Feb. 21, 2020	Feb. 14, 2020	Feb. 10, 2020	Sep. 17, 2019	Aug. 16, 2019	Mar. 08, 2019
Schedule of Investments [Line Items]
Investment commitment	$ 314,461	$ 314,461		$ 314,461		$ 608,851
Funded Investment, outstanding	283,292	283,292		283,292		478,634
Development property investments, Fair Value	316,254	316,254		316,254		549,684
Cash consideration				26,249	$ 129,377
Development property investment, assets	377,900	377,900		377,900
Development property investment, liabilities	341,700	341,700		$ 341,700
Development Property Investments [Member]
Schedule of Investments [Line Items]
Number of investments | property				17
Put option purchase price terms				The put, if exercised, requires the Company to purchase the member’s interest at the original purchase price plus a yield of 4.5% on such purchase price.
Development Property Investments [Member] | Class A Membership Units [Member] | New Haven [Member] | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage																	100.00%
Development Property Investments [Member] | Class A Membership Units [Member] | Jacksonville 2 [Member] | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage																100.00%
Development Property Investments [Member] | Class A Membership Units [Member] | Miami 4, Miami 5, Miami 6, Miami 7 and Miami 8 [Member} | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage															100.00%
Development Property Investments [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Number of investments | property				29
Investment commitment	$ 259,490	$ 259,490		$ 259,490		553,880
Equity method investment, ownership percentage	49.90%	49.90%		49.90%
Mortgage loans on real estate, interest rate				6.90%
Mortgage loans on real estate, periodic payment terms				typically have a term of 72 months
Development property investments, Fair Value	$ 253,432	$ 253,432		$ 253,432		490,651
Issuance of Operating Company ("OC") Units				8,000
In-place leases	7,500	7,500		7,500
Development property investment, assets	377,900	377,900		377,900		592,300
Development property investment, liabilities	341,700	341,700		341,700		531,700
Development property investment, revenue		1,900	$ 2,300	4,700	4,500
Development property investment, operating expenses		1,100	$ 2,700	2,700	$ 6,400
Development Property Investments [Member] | Loan Investments [Member] | Atlanta 4 [Member]
Schedule of Investments [Line Items]
Investment commitment						13,678
Development property investments, Fair Value						17,082
Development Property Investments [Member] | Loan Investments [Member] | Houston [Member]
Schedule of Investments [Line Items]
Investment commitment	14,825	14,825		14,825		14,825
Funded Investment, outstanding	14,800	14,800		14,800
Development property investments, Fair Value	15,661	15,661		15,661		17,820
Development Property Investments [Member] | Loan Investments [Member] | Miami [Member]
Schedule of Investments [Line Items]
Land						3,900
Construction-in-progress						16,500
Development Property Investments [Member] | Loan Investments [Member] | Philadelphia [Member]
Schedule of Investments [Line Items]
Investment commitment	14,338	14,338		14,338		14,338
Funded Investment, outstanding	11,500	11,500		11,500
Development property investments, Fair Value	$ 11,313	11,313		11,313		11,807
Development Property Investments [Member] | Loan Investments [Member] | Raleigh [Member]
Schedule of Investments [Line Items]
Investment commitment						8,792
Development property investments, Fair Value						8,593
Development Property Investments [Member] | Loan Investments [Member] | Jacksonville 3 [Member]
Schedule of Investments [Line Items]
Investment commitment						8,096
Development property investments, Fair Value						10,129
Development Property Investments [Member] | Loan Investments [Member] | New York City 2 [Member]
Schedule of Investments [Line Items]
Investment commitment						27,982
Development property investments, Fair Value						31,047
Development Property Investments [Member] | Loan Investments [Member] | Class A Membership Units [Member] | Charlotte II, Knoxville, Louisville I, Atlanta III, Atlanta V And Atlanta VI [Member] | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage														100.00%
Development Property Investments [Member] | Loan Investments [Member] | Class A Membership Units [Member] | Fort Lauderdale And Boston 2 [Member] | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage													100.00%
Development Property Investments [Member] | Loan Investments [Member] | Class A Membership Units [Member] | Atlanta 4 [Member] | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage												100.00%
Development Property Investments [Member] | Loan Investments [Member] | Class A Membership Units [Member] | Raleigh [Member] | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage										100.00%	100.00%
Development Property Investments [Member] | Loan Investments [Member] | Class A Membership Units [Member] | Minneapolis 1, Minneapolis 2, and Minneapolis 3 [Member] | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage									100.00%
Development Property Investments [Member] | Loan Investments [Member] | Class A Membership Units [Member] | New York City 2 [Member] | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage								100.00%
Development Property Investments [Member] | Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Number of investments | property	5
Investment commitment	$ 54,971	$ 54,971		$ 54,971		$ 54,971
Equity method investment, ownership percentage	90.00%	90.00%		90.00%		90.00%
Development property investments, Fair Value	$ 62,822	$ 62,822		$ 62,822		$ 59,033
Development Property Investments [Member] | Preferred Equity Investments [Member] | Minimum [Member]
Schedule of Investments [Line Items]
Percentage of financing provided by a traditional bank				60.00%
Development Property Investments [Member] | Preferred Equity Investments [Member] | Maximum [Member]
Schedule of Investments [Line Items]
Percentage of financing provided by a traditional bank				70.00%
Five Development Property Investments [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
In-place leases, estimated useful life				12 months
Five Development Property Investments [Member] | Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Number of investments | property				5
Investment commitment	55,000	55,000		$ 55,000
Development Property Investment or Bridge Investment [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Development property investments, Fair Value	255,500	255,500		255,500		125,700
Acquisition date basis of investment	296,100	296,100		296,100		138,900
Cash consideration				30,000		10,500
In-place leases						5,100
Development Property Investment or Bridge Investment [Member] | Loan Investments [Member] | Class A Membership Units [Member] | Orlando 3 and Denver 1 [Member] | Limited Liability Company that Owned the Property [Member]
Schedule of Investments [Line Items]
Minority interest, ownership percentage							100.00%
Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	283,292	283,292		283,292		478,634
Funded Investment [Member] | Development Property Investments [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	223,774	223,774		223,774		422,034
Funded Investment [Member] | Development Property Investments [Member] | Loan Investments [Member] | Atlanta 4 [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding						13,497
Funded Investment [Member] | Development Property Investments [Member] | Loan Investments [Member] | Houston [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	14,825	14,825		14,825		14,825
Funded Investment [Member] | Development Property Investments [Member] | Loan Investments [Member] | Philadelphia [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	11,536	11,536		11,536		11,536
Funded Investment [Member] | Development Property Investments [Member] | Loan Investments [Member] | Raleigh [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding						8,789
Funded Investment [Member] | Development Property Investments [Member] | Loan Investments [Member] | Jacksonville 3 [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding						7,751
Funded Investment [Member] | Development Property Investments [Member] | Loan Investments [Member] | New York City 2 [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding						28,974
Funded Investment [Member] | Development Property Investments [Member] | Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Funded Investment, outstanding	$ 59,518	$ 59,518		$ 59,518		$ 56,600

SELF-STORAGE REAL ESTATE OWNE_2

SELF-STORAGE REAL ESTATE OWNED (Schedule of Investments) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Investment commitment	$ 314,461	$ 608,851
Funded Investment	283,292	478,634
Development property investments, Fair Value	316,254	549,684
Total investments	316,254	549,684
Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	283,292	478,634
Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	52,450	136,104
Development Property Investments [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment commitment	259,490	553,880
Development property investments, Fair Value	$ 253,432	$ 490,651
Equity method investment, ownership percentage	49.90%
Percentage of completion of construction	40.00%	40.00%
Equity method investment percentage of additional equity acquired	50.10%
Development Property Investments [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	$ 223,774	$ 422,034
Development Property Investments [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	51,801	135,455
Development Property Investments [Member] | Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Investment commitment	54,971	54,971
Development property investments, Fair Value	$ 62,822	$ 59,033
Equity method investment, ownership percentage	90.00%	90.00%
Preferred return on investment, percentage	6.90%	6.90%
Transaction fee, percentage of total project cost	1.00%	1.00%
Profits interest, percentage of total project cost	49.90%	49.90%
Development Property Investments [Member] | Preferred Equity Investments [Member] | Minimum [Member]
Schedule of Investments [Line Items]
Percentage of financing provided by a traditional bank	60.00%
Development Property Investments [Member] | Preferred Equity Investments [Member] | Maximum [Member]
Schedule of Investments [Line Items]
Percentage of financing provided by a traditional bank	70.00%
Development Property Investments [Member] | Preferred Equity Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	$ 59,518	$ 56,600
Development Property Investments [Member] | Preferred Equity Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 649	$ 649
Development Property Investments [Member] | Milwaukee [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	7/2/2015	7/2/2015
Investment commitment	$ 7,650	$ 7,650
Development property investments, Fair Value	8,316	8,884
Development Property Investments [Member] | Milwaukee [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	7,648	7,648
Development Property Investments [Member] | Milwaukee [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 2	$ 2
Development Property Investments [Member] | Raleigh [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		8/14/2015
Investment commitment		$ 8,792
Development property investments, Fair Value		8,593
Development Property Investments [Member] | Raleigh [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		8,789
Development Property Investments [Member] | Raleigh [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 3
Development Property Investments [Member] | Austin [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	10/27/2015	10/27/2015
Investment commitment	$ 8,658	$ 8,658
Development property investments, Fair Value	8,071	8,099
Development Property Investments [Member] | Austin [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	8,184	8,136
Development Property Investments [Member] | Austin [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 474	$ 522
Development Property Investments [Member] | Charlotte 2 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		9/20/2016
Investment commitment		$ 12,888
Development property investments, Fair Value		13,984
Development Property Investments [Member] | Charlotte 2 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		12,677
Development Property Investments [Member] | Charlotte 2 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 211
Development Property Investments [Member] | Atlanta 3 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		1/18/2017
Investment commitment		$ 14,115
Development property investments, Fair Value		16,130
Development Property Investments [Member] | Atlanta 3 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		13,297
Development Property Investments [Member] | Atlanta 3 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 818
Development Property Investments [Member] | Atlanta 4 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		1/31/2017
Investment commitment		$ 13,678
Development property investments, Fair Value		17,082
Development Property Investments [Member] | Atlanta 4 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		13,497
Development Property Investments [Member] | Atlanta 4 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 181
Development Property Investments [Member] | Orlando 3 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		2/24/2017
Investment commitment		$ 8,056
Development property investments, Fair Value		9,725
Development Property Investments [Member] | Orlando 3 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		7,767
Development Property Investments [Member] | Orlando 3 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 289
Development Property Investments [Member] | New Orleans [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	2/24/2017	2/24/2017
Investment commitment	$ 12,549	$ 12,549
Development property investments, Fair Value	15,017	14,504
Development Property Investments [Member] | New Orleans [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	12,371	12,021
Development Property Investments [Member] | New Orleans [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 178	$ 528
Development Property Investments [Member] | Atlanta 5 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		2/27/2017
Investment commitment		$ 17,492
Development property investments, Fair Value		19,970
Development Property Investments [Member] | Atlanta 5 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		17,492
Development Property Investments [Member] | Atlanta 5 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 0
Development Property Investments [Member] | Fort Lauderdale [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		3/1/2017
Investment commitment		$ 9,952
Development property investments, Fair Value		13,635
Development Property Investments [Member] | Fort Lauderdale [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		9,383
Development Property Investments [Member] | Fort Lauderdale [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 569
Development Property Investments [Member] | Houston [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	3/1/2017	3/1/2017
Investment commitment	$ 14,825	$ 14,825
Funded Investment	14,800
Development property investments, Fair Value	15,661	17,820
Accrued interest receivable	1,800	900
Development Property Investments [Member] | Houston [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	14,825	14,825
Development Property Investments [Member] | Houston [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 0
Development Property Investments [Member] | Louisville 1 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		4/14/2017
Investment commitment		$ 8,523
Development property investments, Fair Value		9,550
Development Property Investments [Member] | Louisville 1 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		7,552
Development Property Investments [Member] | Louisville 1 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 971
Development Property Investments [Member] | Denver 1 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		4/20/2017
Investment commitment		$ 9,806
Development property investments, Fair Value		10,947
Development Property Investments [Member] | Denver 1 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		9,616
Development Property Investments [Member] | Denver 1 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 190
Development Property Investments [Member] | Denver 2 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		4/20/2017
Investment commitment		$ 11,164
Development property investments, Fair Value		12,383
Development Property Investments [Member] | Denver 2 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		11,009
Development Property Investments [Member] | Denver 2 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 155
Development Property Investments [Member] | Atlanta 6 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		5/2/2017
Investment commitment		$ 12,543
Development property investments, Fair Value		14,744
Development Property Investments [Member] | Atlanta 6 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		12,025
Development Property Investments [Member] | Atlanta 6 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 518
Development Property Investments [Member] | Tampa 2 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	5/2/2017	5/2/2017
Investment commitment	$ 8,091	$ 8,091
Development property investments, Fair Value	9,444	9,196
Development Property Investments [Member] | Tampa 2 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	7,984	7,644
Development Property Investments [Member] | Tampa 2 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 107	$ 447
Development Property Investments [Member] | Tampa 3 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	5/19/2017	5/19/2017
Investment commitment	$ 9,224	$ 9,224
Development property investments, Fair Value	10,561	10,086
Development Property Investments [Member] | Tampa 3 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	8,618	8,326
Development Property Investments [Member] | Tampa 3 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 606	$ 898
Development Property Investments [Member] | Tampa 4 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	6/12/2017	6/12/2017
Investment commitment	$ 10,266	$ 10,266
Development property investments, Fair Value	13,317	12,673
Development Property Investments [Member] | Tampa 4 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	10,014	9,614
Development Property Investments [Member] | Tampa 4 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 252	$ 652
Development Property Investments [Member] | Baltimore 1 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		6/19/2017
Investment commitment		$ 10,775
Development property investments, Fair Value		13,581
Development Property Investments [Member] | Baltimore 1 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		11,010
Development Property Investments [Member] | Baltimore 1 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 274
Development Property Investments [Member] | Knoxville [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		6/28/2017
Investment commitment		$ 9,115
Development property investments, Fair Value		10,355
Development Property Investments [Member] | Knoxville [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		8,628
Development Property Investments [Member] | Knoxville [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 487
Development Property Investments [Member] | Boston 1 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	6/29/2017	6/29/2017
Investment commitment	$ 0	$ 0
Development property investments, Fair Value	3,850	3,361
Development Property Investments [Member] | Boston 1 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	0	0
Development Property Investments [Member] | Boston 1 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 0
Development Property Investments [Member] | New York City 2 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		6/30/2017
Investment commitment		$ 27,982
Development property investments, Fair Value		31,047
Development Property Investments [Member] | New York City 2 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		28,974
Development Property Investments [Member] | New York City 2 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 665
Development Property Investments [Member] | Jacksonville 3 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		7/27/2017
Investment commitment		$ 8,096
Development property investments, Fair Value		10,129
Development Property Investments [Member] | Jacksonville 3 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		7,751
Development Property Investments [Member] | Jacksonville 3 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 345
Development Property Investments [Member] | Orlando 4 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	8/30/2017	8/30/2017
Investment commitment	$ 9,037	$ 9,037
Development property investments, Fair Value	10,376	10,251
Development Property Investments [Member] | Orlando 4 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	8,329	8,107
Development Property Investments [Member] | Orlando 4 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 708	$ 930
Development Property Investments [Member] | Los Angeles 1 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	9/14/2017	9/14/2017
Investment commitment	$ 28,750	$ 28,750
Development property investments, Fair Value	11,143	10,347
Development Property Investments [Member] | Los Angeles 1 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	10,923	10,157
Development Property Investments [Member] | Los Angeles 1 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 17,827	$ 18,593
Development Property Investments [Member] | Miami 1 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	9/14/2017	9/14/2017
Investment commitment	$ 14,657	$ 14,657
Development property investments, Fair Value	15,657	13,373
Development Property Investments [Member] | Miami 1 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	14,463	12,618
Development Property Investments [Member] | Miami 1 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 194	$ 2,039
Development Property Investments [Member] | Louisville 2 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		9/28/2017
Investment commitment		$ 9,940
Development property investments, Fair Value		11,688
Development Property Investments [Member] | Louisville 2 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		9,530
Development Property Investments [Member] | Louisville 2 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 410
Development Property Investments [Member] | Miami 2 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	10/12/2017	10/12/2017
Investment commitment	$ 0	$ 9,459
Development property investments, Fair Value	1,459	1,280
Development Property Investments [Member] | Miami 2 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	1,661	1,494
Development Property Investments [Member] | Miami 2 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 8,045
Development Property Investments [Member] | New York City 3 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	10/30/2017	10/30/2017
Investment commitment	$ 0	$ 15,301
Development property investments, Fair Value	7,916	6,383
Development Property Investments [Member] | New York City 3 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	8,261	6,776
Development Property Investments [Member] | New York City 3 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 8,822
Development Property Investments [Member] | Miami 3 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	11/16/2017	11/16/2017
Investment commitment	$ 20,168	$ 20,168
Development property investments, Fair Value	21,914	12,898
Development Property Investments [Member] | Miami 3 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	19,093	12,086
Development Property Investments [Member] | Miami 3 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 1,745	$ 8,413
Development Property Investments [Member] | Minneapolis 1 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		11/21/2017
Investment commitment		$ 12,674
Development property investments, Fair Value		12,290
Development Property Investments [Member] | Minneapolis 1 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		10,684
Development Property Investments [Member] | Minneapolis 1 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 1,990
Development Property Investments [Member] | Boston 2 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		12/1/2017
Investment commitment		$ 8,771
Development property investments, Fair Value		10,024
Development Property Investments [Member] | Boston 2 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		7,918
Development Property Investments [Member] | Boston 2 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 853
Development Property Investments [Member] | New York City 4 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	12/15/2017	12/15/2017
Investment commitment	$ 10,591	$ 10,591
Development property investments, Fair Value	11,435	7,528
Development Property Investments [Member] | New York City 4 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	9,747	6,705
Development Property Investments [Member] | New York City 4 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 844	$ 3,886
Development Property Investments [Member] | Boston 3 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		12/27/2017
Investment commitment		$ 10,174
Development property investments, Fair Value		2,674
Development Property Investments [Member] | Boston 3 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		2,757
Development Property Investments [Member] | Boston 3 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 7,417
Development Property Investments [Member] | New York City 5 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	12/28/2017	12/28/2017
Investment commitment	$ 16,073	$ 16,073
Development property investments, Fair Value	17,646	16,373
Development Property Investments [Member] | New York City 5 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	16,064	13,817
Development Property Investments [Member] | New York City 5 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 9	$ 2,256
Development Property Investments [Member] | Minneapolis 2 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		2/8/2018
Investment commitment		$ 10,543
Development property investments, Fair Value		11,763
Development Property Investments [Member] | Minneapolis 2 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		9,904
Development Property Investments [Member] | Minneapolis 2 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 639
Development Property Investments [Member] | Philadelphia [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	3/30/2018	3/30/2018
Investment commitment	$ 14,338	$ 14,338
Funded Investment	11,500
Development property investments, Fair Value	11,313	11,807
Accrued interest receivable	4,500	4,500
Development Property Investments [Member] | Philadelphia [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	11,536	11,536
Development Property Investments [Member] | Philadelphia [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 3,264	$ 3,263
Development Property Investments [Member] | Minneapolis 3 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date		4/6/2018
Investment commitment		$ 12,883
Development property investments, Fair Value		12,043
Development Property Investments [Member] | Minneapolis 3 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment		10,337
Development Property Investments [Member] | Minneapolis 3 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment		$ 2,546
Development Property Investments [Member] | Miami 9 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	5/1/2018	5/1/2018
Investment commitment	$ 0	$ 12,421
Development property investments, Fair Value	3,639	3,427
Development Property Investments [Member] | Miami 9 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	3,877	3,560
Development Property Investments [Member] | Miami 9 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 9,006
Development Property Investments [Member] | Atlanta 7 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	5/15/2018	5/15/2018
Investment commitment	$ 9,418	$ 9,418
Development property investments, Fair Value	9,948	7,683
Development Property Investments [Member] | Atlanta 7 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	8,502	6,563
Development Property Investments [Member] | Atlanta 7 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 916	$ 2,855
Development Property Investments [Member] | Kansas City [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	5/23/2018	5/23/2018
Investment commitment	$ 9,968	$ 9,968
Development property investments, Fair Value	10,489	9,663
Development Property Investments [Member] | Kansas City [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	8,754	8,235
Development Property Investments [Member] | Kansas City [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 1,214	$ 1,733
Development Property Investments [Member] | Orlando 5 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	6/7/2018	6/7/2018
Investment commitment	$ 12,969	$ 12,969
Development property investments, Fair Value	13,885	11,780
Development Property Investments [Member] | Orlando 5 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	12,057	10,340
Development Property Investments [Member] | Orlando 5 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 912	$ 2,629
Development Property Investments [Member] | Los Angeles 2 [Member] | Loan Investments [Member] | Minimum [Member]
Schedule of Investments [Line Items]
Percentage of Financing not offered by the bank	30.00%	30.00%
Percentage of financing provided by a traditional bank	60.00%	60.00%
Development Property Investments [Member] | Los Angeles 2 [Member] | Loan Investments [Member] | Maximum [Member]
Schedule of Investments [Line Items]
Percentage of Financing not offered by the bank	40.00%	40.00%
Percentage of financing provided by a traditional bank	70.00%	70.00%
Development Property Investments [Member] | Los Angeles 2 [Member] | Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	6/12/2018	6/12/2018
Investment commitment	$ 9,298	$ 9,298
Development property investments, Fair Value	10,384	9,403
Development Property Investments [Member] | Los Angeles 2 [Member] | Preferred Equity Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	9,659	9,173
Development Property Investments [Member] | Los Angeles 2 [Member] | Preferred Equity Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 649	$ 649
Development Property Investments [Member] | Baltimore 2 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	11/16/2018	11/16/2018
Investment commitment	$ 0	$ 9,247
Development property investments, Fair Value	690	709
Development Property Investments [Member] | Baltimore 2 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	785	757
Development Property Investments [Member] | Baltimore 2 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 8,490
Development Property Investments [Member] | New York City 6 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	3/1/2019	3/1/2019
Investment commitment	$ 18,796	$ 18,796
Development property investments, Fair Value	4,311	3,122
Development Property Investments [Member] | New York City 6 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	4,297	3,168
Development Property Investments [Member] | New York City 6 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 14,499	$ 15,628
Development Property Investments [Member] | Stamford [Member] | Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	3/15/2019	3/15/2019
Investment commitment	$ 2,904	$ 2,904
Development property investments, Fair Value	5,479	4,952
Development Property Investments [Member] | Stamford [Member] | Preferred Equity Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	3,222	3,064
Development Property Investments [Member] | Stamford [Member] | Preferred Equity Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 0
Development Property Investments [Member] | New York City 7 [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	4/18/2019	4/18/2019
Investment commitment	$ 23,462	$ 23,462
Development property investments, Fair Value	17,374	7,067
Development Property Investments [Member] | New York City 7 [Member] | Loan Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	15,781	7,304
Development Property Investments [Member] | New York City 7 [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 8,050	$ 16,287
Development Property Investments [Member] | New York City 8 [Member] | Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	5/8/2019	5/8/2019
Investment commitment	$ 21,000	$ 21,000
Development property investments, Fair Value	23,492	22,359
Development Property Investments [Member] | New York City 8 [Member] | Preferred Equity Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	23,073	21,945
Development Property Investments [Member] | New York City 8 [Member] | Preferred Equity Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 0
Development Property Investments [Member] | New York City 9 [Member] | Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	7/11/2019	7/11/2019
Investment commitment	$ 13,095	$ 13,095
Development property investments, Fair Value	14,177	13,489
Development Property Investments [Member] | New York City 9 [Member] | Preferred Equity Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	14,218	13,526
Development Property Investments [Member] | New York City 9 [Member] | Preferred Equity Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 0
Development Property Investments [Member] | New York City 10 [Member] | Preferred Equity Investments [Member]
Schedule of Investments [Line Items]
Investment closing date	8/21/2019	8/21/2019
Investment commitment	$ 8,674	$ 8,674
Development property investments, Fair Value	9,290	8,830
Development Property Investments [Member] | New York City 10 [Member] | Preferred Equity Investments [Member] | Funded Investment [Member]
Schedule of Investments [Line Items]
Funded Investment	9,346	8,892
Development Property Investments [Member] | New York City 10 [Member] | Preferred Equity Investments [Member] | Unfunded Commitment [Member]
Schedule of Investments [Line Items]
Investment commitment	$ 0	$ 0

SELF-STORAGE REAL ESTATE OWNE_3

SELF-STORAGE REAL ESTATE OWNED (Schedule of Changes in Fair Value of Investments) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Funded investment, net of unamortized origination fee	$ 283,292	$ 478,634
Adjustments:
Unamortized origination and other fees	(3,292)	(5,633)
Net unrealized gain (loss) on investments	36,340	76,767
Other	(86)	(84)
Total investments	$ 316,254	$ 549,684

SELF-STORAGE REAL ESTATE OWNE_4

SELF-STORAGE REAL ESTATE OWNED (Real Estate Investment, Impact in Consolidated Balance Sheet , Disclosure) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Self-storage real estate owned	$ 513,993	$ 230,844
Real Estate Investment [Member]
Schedule of Investments [Line Items]
Land	72,262	29,430
Building and improvements	448,796	186,295
In-place leases	16,128	8,629
Property equipment	217	122
Construction-in-progress	0	16,460
Accumulated depreciation and amortization	(23,410)	(10,092)
Self-storage real estate owned	513,993	$ 230,844
Development Property Investments [Member] | Loan Investments [Member]
Schedule of Investments [Line Items]
In-place leases	$ 7,500

FAIR VALUE OF FINANCIAL INSTR_3

FAIR VALUE OF FINANCIAL INSTRUMENTS (Narrative) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)property	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Percentage of construction completion threshold percentage when most entrepreneurial profit is earned			40.00%
Investment owned, unrecognized unrealized appreciation (depreciation), net	$ 36.3		$ 36.3		$ 76.8
Gains or losses attributable to changes in instrument-specific credit risk	$ 0	$ 0	$ 0	$ 0
Development Property Investments [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Number of investments | property			17
Minimum [Member] | Three Development Properties [Member]
Fair Value, Concentration of Risk, Financial Statement Captions [Line Items]
Percentage of completion of construction			40.00%

FAIR VALUE OF FINANCIAL INSTR_4

FAIR VALUE OF FINANCIAL INSTRUMENTS (Summary of Significant Unobservable Inputs used to Value Investments) (Details)	9 Months Ended	12 Months Ended
	Sep. 30, 2020YUSD ($)	Dec. 31, 2019USD ($)Y
Development Property Investments [Member] | Minimum [Member] | Income Approach Analysis [Member] | Market Yields/Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.0694	0.0689
Development Property Investments [Member] | Minimum [Member] | Income Approach Analysis [Member] | Exit Date [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.83	1.50
Development Property Investments [Member] | Minimum [Member] | Option Pricing Model [Member] | Volatility [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.6703	0.6095
Development Property Investments [Member] | Minimum [Member] | Option Pricing Model [Member] | Market Yields/Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.0825	0.0775
Development Property Investments [Member] | Minimum [Member] | Option Pricing Model [Member] | Exit Date [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.83	1.50
Development Property Investments [Member] | Minimum [Member] | Option Pricing Model [Member] | Capitalization Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.0525	0.0475
Development Property Investments [Member] | Maximum [Member] | Income Approach Analysis [Member] | Market Yields/Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.0916	0.1016
Development Property Investments [Member] | Maximum [Member] | Income Approach Analysis [Member] | Exit Date [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	5.94	6.69
Development Property Investments [Member] | Maximum [Member] | Option Pricing Model [Member] | Volatility [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.9675	0.9383
Development Property Investments [Member] | Maximum [Member] | Option Pricing Model [Member] | Market Yields/Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.0850	0.0875
Development Property Investments [Member] | Maximum [Member] | Option Pricing Model [Member] | Exit Date [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	5.94	6.69
Development Property Investments [Member] | Maximum [Member] | Option Pricing Model [Member] | Capitalization Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.0550	0.0575
Development Property Investments [Member] | Weighted Average [Member] | Income Approach Analysis [Member] | Market Yields/Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	0.0810	0.0839
Development Property Investments [Member] | Weighted Average [Member] | Income Approach Analysis [Member] | Exit Date [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	3.65	3.40
Development Property Investments [Member] | Weighted Average [Member] | Option Pricing Model [Member] | Volatility [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs | $	0.7851	0.7324
Development Property Investments [Member] | Weighted Average [Member] | Option Pricing Model [Member] | Market Yields/Discount Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs | $	0.0843	0.0846
Development Property Investments [Member] | Weighted Average [Member] | Option Pricing Model [Member] | Exit Date [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs	3.65	3.40
Development Property Investments [Member] | Weighted Average [Member] | Option Pricing Model [Member] | Capitalization Rate [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Development property investments and bridge investments, unobservable inputs | $	0.0543	0.0546
Development Property Investments [Member] | Loan Investments [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Percentage of completion of construction	40.00%	40.00%
Thirty Eight Development Properties [Member] | Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Percentage of completion of construction		40.00%
Thirty Eight Development Properties [Member] | Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Percentage of completion of construction		100.00%
Twenty Development Properties [Member] | Minimum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Percentage of completion of construction	40.00%
Twenty Development Properties [Member] | Maximum [Member]
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Percentage of completion of construction	100.00%

FAIR VALUE OF FINANCIAL INSTR_5

FAIR VALUE OF FINANCIAL INSTRUMENTS (Schedule of Change in Fair Value of Investments Due to Change in Market Yield Discount Rates) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Up 25 Basis Points [Member]
Investments in and Advances to Affiliates [Line Items]
Increase (decrease) in fair value of investments	$ (1.1)	$ (2.1)
Down 25 Basis Points [Member]
Investments in and Advances to Affiliates [Line Items]
Increase (decrease) in fair value of investments	0.5	2.2
Up 50 basis points [Member]
Investments in and Advances to Affiliates [Line Items]
Increase (decrease) in fair value of investments	(2.2)	(4.2)
Down 50 Basis Points [Member]
Investments in and Advances to Affiliates [Line Items]
Increase (decrease) in fair value of investments	$ 0.5	$ 4.5

FAIR VALUE OF FINANCIAL INSTR_6

FAIR VALUE OF FINANCIAL INSTRUMENTS (Schedule of Change in Fair Value of Investments Due to Change in Capitalization Rates) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Up 25 Basis Points [Member]
Investments in and Advances to Affiliates [Line Items]
Increase (decrease) in fair value of investments	$ (4.8)	$ (10.2)
Down 25 Basis Points [Member]
Investments in and Advances to Affiliates [Line Items]
Increase (decrease) in fair value of investments	5.2	11.1
Up 50 basis points [Member]
Investments in and Advances to Affiliates [Line Items]
Increase (decrease) in fair value of investments	(9.5)	(19.4)
Down 50 Basis Points [Member]
Investments in and Advances to Affiliates [Line Items]
Increase (decrease) in fair value of investments	$ 11	$ 23.4

FAIR VALUE OF FINANCIAL INSTR_7

FAIR VALUE OF FINANCIAL INSTRUMENTS (Changes in Investments that Use Level 3 Inputs) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
FAIR VALUE OF FINANCIAL INSTRUMENTS [Abstract]
Balance as of beginning of period			$ 549,684	$ 457,947
Realized gains			0
Unrealized losses	$ 4,540	$ 7,974	(5,630)	28,847
Fundings of principal and change in unamortized origination fees			26,354	126,100
Repayments of loans			(13,878)	(361)
Payment-in-kind interest			15,219	22,069
Reclassification of self-storage real estate owned			(255,495)	(125,715)
Net transfers in or out of Level 3			0	0
Balance at end of period	$ 316,254	$ 508,887	$ 316,254	$ 508,887

INVESTMENT IN SELF-STORAGE RE_3

INVESTMENT IN SELF-STORAGE REAL ESTATE VENTURE (Narrative) (Details) $ in Thousands	Sep. 30, 2020USD ($)property	Mar. 04, 2020USD ($)	Jan. 31, 2020USD ($)	Sep. 17, 2019USD ($)	Feb. 27, 2019USD ($)	Apr. 30, 2019USD ($)	Sep. 30, 2020USD ($)	Sep. 30, 2020USD ($)property	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)property	Dec. 31, 2016USD ($)	Jun. 24, 2020USD ($)	Jun. 23, 2020	Nov. 07, 2019USD ($)	Nov. 06, 2019	Jan. 28, 2019USD ($)	Jan. 27, 2019	Mar. 31, 2016USD ($)	Mar. 07, 2016USD ($)
Investment In Real Estate Venture [Line Items]
Investment in and advances to self-storage real estate venture	$ 4,053						$ 4,053	$ 4,053		$ 11,247
Development property investment, assets	377,900						377,900	377,900
Development property investment, liabilities	341,700						341,700	341,700
Investment commitment	314,461						314,461	314,461		608,851
Funded investment, net of unamortized origination fee	283,292						283,292	283,292		478,634
Return of capital from unconsolidated self-storage real estate venture								$ 4,683	$ 3,833
Development Property Investments [Member]
Investment In Real Estate Venture [Line Items]
Number of investments | property								17
SL1 Venture [Member]
Investment In Real Estate Venture [Line Items]
Investment in and advances to self-storage real estate venture	0						0	$ 0		300
Joint venture agreement percentage of priority distribution, percentage of committed principal amount								1.00%
Development property investment, assets	95,300						95,300	$ 95,300
Development property investment, liabilities	41,000						41,000	41,000
Investment, income (loss)							(1,400)	(3,000)
Investment commitment	$ 12,300						12,300	12,300		$ 12,300
Transaction expenses								200
Notional Amount						$ 36,100
Interest rate swap, maturity date						Apr. 1, 2021
SL1 Venture [Member] | Raleigh [Member]
Investment In Real Estate Venture [Line Items]
Loan maturity date			Feb. 27, 2022
SL1 Venture [Member] | Put Option [Member]
Investment In Real Estate Venture [Line Items]
Number of investments | property	4
Recognized loss							1,900	$ 1,900
SL1 Venture [Member] | London Interbank Offered Rate Libor Swap Rate [Member]
Investment In Real Estate Venture [Line Items]
Interest rate swap, fixed rate						2.29%
SL1 Venture [Member] | Term Loans [Member] | London Interbank Offered Rate (LIBOR) [Member] | Raleigh [Member]
Investment In Real Estate Venture [Line Items]
Debt instrument, basis spread on variable rate			2.15%
SL1 Venture [Member] | Development Property Investments [Member]
Investment In Real Estate Venture [Line Items]
Number of investments | property								5		6
SL1 Venture [Member] | Eight Properties [Member]
Investment In Real Estate Venture [Line Items]
Investment commitment	$ 123,300						123,300	$ 123,300		$ 81,400
Number of investments | property										8
SL1 Venture [Member] | Four Properties [Member]
Investment In Real Estate Venture [Line Items]
Loan maturity date					Feb. 27, 2022
SL1 Venture [Member] | Four Properties [Member] | London Interbank Offered Rate (LIBOR) [Member]
Investment In Real Estate Venture [Line Items]
Debt instrument, basis spread on variable rate					2.15%
SL1 Venture [Member] | Four Properties [Member] | Term Loans [Member]
Investment In Real Estate Venture [Line Items]
Issuance of debt, aggregate loan proceeds					$ 36,100
SL1 Venture [Member] | Parent Company [Member]
Investment In Real Estate Venture [Line Items]
Equity method investment, ownership percentage																			10.00%
Investment owned, aggregate committed principal amount																		$ 41,900
Investment, income (loss)							(100)	(300)
Investment commitment																		8,100
Investment in joint venture, fair value																		7,700
Funded investment, net of unamortized origination fee																		$ 8,100	$ 12,200
Return of capital from unconsolidated self-storage real estate venture											$ 7,300
SL1 Venture [Member] | Parent Company [Member] | Washington DC [Member]
Investment In Real Estate Venture [Line Items]
Proceeds from issuance of debt				$ 1,700
SL1 Venture [Member] | Parent Company [Member] | Raleigh [Member]
Investment In Real Estate Venture [Line Items]
Proceeds from issuance of debt			$ 300
SL1 Venture [Member] | Parent Company [Member] | Eight Properties [Member]
Investment In Real Estate Venture [Line Items]
Investment commitment	12,300						12,300	$ 12,300
SL1 Venture [Member] | Parent Company [Member] | Four Properties [Member]
Investment In Real Estate Venture [Line Items]
Proceeds from issuance of debt					2,100
IRR Threshold One [Member]
Investment In Real Estate Venture [Line Items]
Agreement metric, internal rate of return								14.00%
Agreement metric, capital distribution percentage to third party								10.00%
Agreement metric, capital distribution percentage								10.00%
IRR Threshold Two [Member]
Investment In Real Estate Venture [Line Items]
Agreement metric, internal rate of return								17.00%
Agreement metric, capital distribution percentage to third party								20.00%
Agreement metric, capital distribution percentage								20.00%
IRR Threshold Three [Member]
Investment In Real Estate Venture [Line Items]
Agreement metric, internal rate of return								20.00%
Agreement metric, capital distribution percentage to third party								30.00%
Agreement metric, capital distribution percentage								30.00%
SL1 Venture - Three Borrowers [Member] | Term Loans [Member] | Raleigh [Member]
Investment In Real Estate Venture [Line Items]
Issuance of debt, aggregate loan proceeds			3,200
SL1 Venture - Three Borrowers [Member] | Parent Company [Member] | Miami 1, Miami 2 and Fort Lauderdale [Member]
Investment In Real Estate Venture [Line Items]
Proceeds from issuance of debt		$ 4,100
Heitman And Large Institutional Co-Investor [Member] | SL1 Venture [Member]
Investment In Real Estate Venture [Line Items]
Investment in and advances to self-storage real estate venture	0						0	$ 0		$ 300									$ 110,000
Equity method investment, ownership percentage																			90.00%
Agreement metric, return multiple								1.48
Heitman And Large Institutional Co-Investor [Member] | SL1 Venture [Member] | Washington DC [Member]
Investment In Real Estate Venture [Line Items]
Proceeds from issuance of debt				$ 15,500
Heitman And Large Institutional Co-Investor [Member] | SL1 Venture - Three Borrowers [Member] | Miami 1, Miami 2 and Fort Lauderdale [Member]
Investment In Real Estate Venture [Line Items]
Proceeds from issuance of debt		$ 36,500
HVP III Storage Lenders Investor, LLC [Member] | SL1 Venture [Member]
Investment In Real Estate Venture [Line Items]
Payment to acquire interest in joint venture											$ 7,300
Investment, income (loss)							(1,300)	$ (2,700)
HVP III Storage Lenders Investor, LLC [Member] | SL1 Venture [Member] | Raleigh [Member]
Investment In Real Estate Venture [Line Items]
Proceeds from issuance of debt			$ 2,700
HVP III Storage Lenders Investor, LLC [Member] | SL1 Venture [Member] | Eight Properties [Member]
Investment In Real Estate Venture [Line Items]
Investment commitment	$ 111,000						$ 111,000	$ 111,000
HVP III Storage Lenders Investor, LLC [Member] | SL1 Venture [Member] | Four Properties [Member]
Investment In Real Estate Venture [Line Items]
Proceeds from issuance of debt					$ 19,000
Loan Investments [Member] | Development Property Investments [Member]
Investment In Real Estate Venture [Line Items]
Equity method investment, ownership percentage	49.90%						49.90%	49.90%
Development property investment, assets	$ 377,900						$ 377,900	$ 377,900		592,300
Development property investment, liabilities	341,700						341,700	341,700		531,700
Investment commitment	$ 259,490						$ 259,490	$ 259,490		553,880
Number of investments | property								29
Loan Investments [Member] | Development Property Investments [Member] | Raleigh [Member]
Investment In Real Estate Venture [Line Items]
Investment commitment										$ 8,792
Loan Investments [Member] | SL1 Venture [Member] | Washington DC [Member]
Investment In Real Estate Venture [Line Items]
Equity method investment, ownership percentage	49.90%						49.90%	49.90%
Loan Investments [Member] | SL1 Venture [Member] | Raleigh [Member]
Investment In Real Estate Venture [Line Items]
Equity method investment, ownership percentage														100.00%	49.90%
Acquisition date basis of investment														$ 9,700
Loan Investments [Member] | SL1 Venture [Member] | Columbia [Member]
Investment In Real Estate Venture [Line Items]
Equity method investment, ownership percentage												100.00%	49.90%
Acquisition date basis of investment												$ 10,300
Loan Investments [Member] | SL1 Venture [Member] | Development Property Investments [Member]
Investment In Real Estate Venture [Line Items]
Equity method investment, ownership percentage	49.90%						49.90%	49.90%		49.90%
Investment commitment	$ 7,828						$ 7,828	$ 7,828		$ 58,973
Loan Investments [Member] | SL1 Venture [Member] | Development Property Investments [Member] | Washington DC [Member]
Investment In Real Estate Venture [Line Items]
Investment commitment	$ 0						$ 0	$ 0		0
Loan Investments [Member] | SL1 Venture [Member] | Development Property Investments [Member] | Columbia [Member]
Investment In Real Estate Venture [Line Items]
Investment commitment										$ 9,199
Loan Investments [Member] | SL1 Venture [Member] | Four Properties [Member]
Investment In Real Estate Venture [Line Items]
Equity method investment, ownership percentage																100.00%	49.90%
Acquisition date basis of investment																$ 57,200
Loan Investments [Member] | SL1 Venture - Three Borrowers [Member] | Miami 1, Miami 2 and Fort Lauderdale [Member]
Investment In Real Estate Venture [Line Items]
Equity method investment, ownership percentage	49.90%						49.90%	49.90%

INVESTMENT IN SELF-STORAGE RE_4

INVESTMENT IN SELF-STORAGE REAL ESTATE VENTURE (Equity Method Investments) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019	Jun. 24, 2020	Jun. 23, 2020	Jan. 28, 2019	Jan. 27, 2019	Mar. 31, 2016
Real Estate Properties [Line Items]
Investment commitment	$ 314,461	$ 608,851
Funded Investment	283,292	478,634
Fair value of investments	316,254	549,684
Funded Investment [Member]
Real Estate Properties [Line Items]
Funded Investment	283,292	478,634
Unfunded Commitment [Member]
Real Estate Properties [Line Items]
Investment commitment	52,450	136,104
SL1 Venture [Member]
Real Estate Properties [Line Items]
Investment commitment	12,300	12,300
SL1 Venture [Member] | Unfunded Commitment [Member]
Real Estate Properties [Line Items]
Investment commitment	$ 40	200
SL1 Venture [Member] | Loan Investments [Member] | Washington DC [Member]
Real Estate Properties [Line Items]
Equity method investment, ownership percentage	49.90%
SL1 Venture [Member] | Loan Investments [Member] | Columbia [Member]
Real Estate Properties [Line Items]
Equity method investment, ownership percentage			100.00%	49.90%
Development Property Investments [Member] | Loan Investments [Member]
Real Estate Properties [Line Items]
Investment commitment	$ 259,490	553,880
Fair value of investments	$ 253,432	$ 490,651
Percentage of completion of construction	40.00%	40.00%
Equity method investment, ownership percentage	49.90%
Development Property Investments [Member] | Loan Investments [Member] | Miami 1 [Member]
Real Estate Properties [Line Items]
Investment Closing Date	9/14/2017	9/14/2017
Investment commitment	$ 14,657	$ 14,657
Fair value of investments	$ 15,657	$ 13,373
Development Property Investments [Member] | Loan Investments [Member] | Miami 2 [Member]
Real Estate Properties [Line Items]
Investment Closing Date	10/12/2017	10/12/2017
Investment commitment	$ 0	$ 9,459
Fair value of investments	1,459	$ 1,280
Development Property Investments [Member] | Loan Investments [Member] | Fort Lauderdale [Member]
Real Estate Properties [Line Items]
Investment Closing Date		3/1/2017
Investment commitment		$ 9,952
Fair value of investments		13,635
Development Property Investments [Member] | Loan Investments [Member] | Funded Investment [Member]
Real Estate Properties [Line Items]
Funded Investment	223,774	422,034
Development Property Investments [Member] | Loan Investments [Member] | Funded Investment [Member] | Miami 1 [Member]
Real Estate Properties [Line Items]
Funded Investment	14,463	12,618
Development Property Investments [Member] | Loan Investments [Member] | Funded Investment [Member] | Miami 2 [Member]
Real Estate Properties [Line Items]
Funded Investment	1,661	1,494
Development Property Investments [Member] | Loan Investments [Member] | Funded Investment [Member] | Fort Lauderdale [Member]
Real Estate Properties [Line Items]
Funded Investment		9,383
Development Property Investments [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Real Estate Properties [Line Items]
Investment commitment	51,801	135,455
Development Property Investments [Member] | Loan Investments [Member] | Unfunded Commitment [Member] | Miami 1 [Member]
Real Estate Properties [Line Items]
Investment commitment	194	2,039
Development Property Investments [Member] | Loan Investments [Member] | Unfunded Commitment [Member] | Miami 2 [Member]
Real Estate Properties [Line Items]
Investment commitment	0	8,045
Development Property Investments [Member] | Loan Investments [Member] | Unfunded Commitment [Member] | Fort Lauderdale [Member]
Real Estate Properties [Line Items]
Investment commitment		569
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member]
Real Estate Properties [Line Items]
Investment commitment	7,828	58,973
Fair value of investments	$ 20,158	$ 72,786
Equity method investment, ownership percentage	49.90%	49.90%
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Miami 1 [Member]
Real Estate Properties [Line Items]
Investment Closing Date	5/14/2015	5/14/2015
Investment commitment	$ 0	$ 13,867
Fair value of investments	$ 1,638	$ 16,222
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Miami 2 [Member]
Real Estate Properties [Line Items]
Investment Closing Date	5/14/2015	5/14/2015
Investment commitment	$ 0	$ 14,849
Fair value of investments	$ 1,702	$ 16,588
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Fort Lauderdale [Member]
Real Estate Properties [Line Items]
Investment Closing Date	9/25/2015	9/25/2015
Investment commitment	$ 0	$ 13,230
Fair value of investments	$ 4,211	$ 17,156
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Washington DC [Member]
Real Estate Properties [Line Items]
Investment Closing Date	4/15/2016	4/15/2016
Investment commitment	$ 0	$ 0
Fair value of investments	$ 3,727	$ 3,339
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | New Jersey [Member]
Real Estate Properties [Line Items]
Investment Closing Date	7/21/2016	7/21/2016
Investment commitment	$ 7,828	$ 7,828
Fair value of investments	8,880	$ 9,036
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Columbia [Member]
Real Estate Properties [Line Items]
Investment Closing Date		9/28/2016
Investment commitment		$ 9,199
Fair value of investments		10,445
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Funded Investment [Member]
Real Estate Properties [Line Items]
Funded Investment	7,471	56,962
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Funded Investment [Member] | Miami 1 [Member]
Real Estate Properties [Line Items]
Funded Investment	0	13,114
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Funded Investment [Member] | Miami 2 [Member]
Real Estate Properties [Line Items]
Funded Investment	0	14,519
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Funded Investment [Member] | Fort Lauderdale [Member]
Real Estate Properties [Line Items]
Funded Investment	0	12,899
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Funded Investment [Member] | Washington DC [Member]
Real Estate Properties [Line Items]
Funded Investment	0	0
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Funded Investment [Member] | New Jersey [Member]
Real Estate Properties [Line Items]
Funded Investment	7,471	7,357
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Funded Investment [Member] | Columbia [Member]
Real Estate Properties [Line Items]
Funded Investment		9,073
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Unfunded Commitment [Member]
Real Estate Properties [Line Items]
Investment commitment	357	2,011
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Unfunded Commitment [Member] | Miami 1 [Member]
Real Estate Properties [Line Items]
Investment commitment	0	753
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Unfunded Commitment [Member] | Miami 2 [Member]
Real Estate Properties [Line Items]
Investment commitment	0	330
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Unfunded Commitment [Member] | Fort Lauderdale [Member]
Real Estate Properties [Line Items]
Investment commitment	0	331
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Unfunded Commitment [Member] | Washington DC [Member]
Real Estate Properties [Line Items]
Investment commitment	0	0
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Unfunded Commitment [Member] | New Jersey [Member]
Real Estate Properties [Line Items]
Investment commitment	357	471
Development Property Investments [Member] | SL1 Venture [Member] | Loan Investments [Member] | Unfunded Commitment [Member] | Columbia [Member]
Real Estate Properties [Line Items]
Investment commitment		126
Eight Properties [Member] | SL1 Venture [Member]
Real Estate Properties [Line Items]
Investment commitment	$ 123,300	$ 81,400
Four Properties [Member] | SL1 Venture [Member] | Loan Investments [Member]
Real Estate Properties [Line Items]
Equity method investment, ownership percentage					100.00%	49.90%
Three Properties [Member] | SL1 Venture [Member] | Loan Investments [Member]
Real Estate Properties [Line Items]
Funded Investment							$ 8,100

VARIABLE INTEREST ENTITIES (Nar

VARIABLE INTEREST ENTITIES (Narrative) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Variable Interest Entity [Line Items]
Assets recorded related to VIEs	$ 316,254	$ 549,684
Investment commitment	314,461	608,851
Funded investment, net of unamortized origination fee	283,292	478,634
Investment in and advances to self-storage real estate venture	4,053	11,247
SL1 Venture [Member]
Variable Interest Entity [Line Items]
Investment commitment	12,300	12,300
Investment in and advances to self-storage real estate venture	0	300
Funded Investment [Member]
Variable Interest Entity [Line Items]
Funded investment, net of unamortized origination fee	283,292	478,634
Unfunded Commitment [Member]
Variable Interest Entity [Line Items]
Investment commitment	52,450	136,104
Unfunded Commitment [Member] | SL1 Venture [Member]
Variable Interest Entity [Line Items]
Investment commitment	$ 40	$ 200

VARIABLE INTEREST ENTITIES (Sch

VARIABLE INTEREST ENTITIES (Schedule of Variable Interest Entities) (Details) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
VARIABLE INTEREST ENTITIES [Abstract]
Assets recorded related to VIEs	$ 316,254	$ 549,684
Unfunded loan commitments to VIEs	52,450	136,104
Maximum exposure to loss	$ 368,704	$ 685,788

DEBT (Summary of Debt) (Details

DEBT (Summary of Debt) (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Secured revolving credit facility carrying value	$ 242,000	$ 162,000
Total Term Loans	41,175	41,175
Term loan debt issuance costs	(202)	(384)
Net Term Loans	40,973	40,791
Total debt	$ 282,973	$ 202,791
Secured revolving credit facility [Member]
Debt Instrument [Line Items]
Maturity Date	Mar. 24, 2023	Mar. 24, 2023
Effective Interest Rate	2.65%	2.65%
Term loan 1 [Member]
Debt Instrument [Line Items]
Maturity Date	Aug. 1, 2021	Aug. 1, 2021
Effective Interest Rate	2.41%	2.41%
Total Term Loans	$ 9,150	$ 9,150
Term loan 2 [Member]
Debt Instrument [Line Items]
Maturity Date	Aug. 1, 2021	Aug. 1, 2021
Effective Interest Rate	2.41%	2.41%
Total Term Loans	$ 7,125	$ 7,125
Term loan 3 [Member]
Debt Instrument [Line Items]
Maturity Date	Aug. 1, 2021	Aug. 1, 2021
Effective Interest Rate	2.41%	2.41%
Total Term Loans	$ 8,625	$ 8,625
Term loan 4 [Member]
Debt Instrument [Line Items]
Maturity Date	Aug. 1, 2021	Aug. 1, 2021
Effective Interest Rate	2.41%	2.41%
Total Term Loans	$ 9,188	$ 9,188
Term loan 5 [Member]
Debt Instrument [Line Items]
Maturity Date	Aug. 1, 2021	Aug. 1, 2021
Effective Interest Rate	2.41%	2.41%
Total Term Loans	$ 7,087	$ 7,087

DEBT (Credit Facility) (Narrati

DEBT (Credit Facility) (Narrative) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Mar. 26, 2020
Line of Credit Facility [Line Items]
Proceeds from lines of credit	$ 74,671	$ 124,261
Credit Facility [Member]
Line of Credit Facility [Line Items]
Long-term line of credit, remaining borrowing capacity	$ 41,800
KeyBank National Association [Member]
Line of Credit Facility [Line Items]
Maturity Date	Mar. 24, 2023
Debt instrument maturity, description	on March 24, 2023 with two one-year extension options to extend the maturity of the facility to March 26, 2025
Debt instrument covenants minimum fixed coverage ratio	1.05
Debt instrument covenants consolidated tangible net worth, minimum	$ 360,500
Debt instrument covenants any additional net offering proceeds percentage included in consolidated tangible net worth	75.00%
Debt instrument covenants threshold amount that limits unhedged variable rate	$ 50,000
Debt instrument covenants unhedged variable rate maximum percentage	40.00%
Debt instrument covenant debt service coverage ratio	2
Minimum borrowing base asset	25
Long term debt outstanding	$ 242,000
Line of credit facility, covenant compliance	As of September 30, 2020, the Company was in compliance with all of its financial covenants of the Amended and Restated Credit Facility.
KeyBank National Association [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Line of credit, current maximum borrowing capacity	$ 283,800
KeyBank National Association [Member] | March 26, 2020 And December 31, 2020 [Member]
Line of Credit Facility [Line Items]
Debt instrument covenants minimum fixed coverage ratio	1.15
Debt instrument covenants liquidity minimal amount	$ 25,000
Minimum borrowing base asset amount	$ 150,000
Minimum borrowing base availability	20.00%
KeyBank National Association [Member] | March 26, 2020 And December 31, 2020 [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument covenant total consolidated indebtedness, maximum percentage of gross asset value	45.00%
KeyBank National Association [Member] | January 1 2021 And March 24 2023 [Member]
Line of Credit Facility [Line Items]
Minimum borrowing base asset amount	$ 250,000
KeyBank National Association [Member] | January 1 2021 And March 24 2023 [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument covenant total consolidated indebtedness, maximum percentage of gross asset value	50.00%
KeyBank National Association [Member] | January 1, 2021 And December 31, 2021 [Member]
Line of Credit Facility [Line Items]
Debt instrument covenants minimum fixed coverage ratio	1.20
Minimum borrowing base availability	40.00%
KeyBank National Association [Member] | January 1, 2022 And Mar 24, 2023 [Member]
Line of Credit Facility [Line Items]
Debt instrument covenants minimum fixed coverage ratio	1.40
Minimum borrowing base availability	60.00%
KeyBank National Association [Member] | After January 1, 2021 [Member]
Line of Credit Facility [Line Items]
Debt instrument covenants liquidity minimal amount	$ 25,000
KeyBank National Association [Member] | Base Rate, Tranche One [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.10%
KeyBank National Association [Member] | Base Rate, Tranche Two [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.50%
KeyBank National Association [Member] | Base Rate, Tranche Three [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.00%
KeyBank National Association [Member] | LIBOR Rate, Tranche One [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.10%
KeyBank National Association [Member] | LIBOR Rate, Tranche Two [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.50%
KeyBank National Association [Member] | LIBOR Rate, Tranche Three [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	3.00%
Maximum [Member] | KeyBank National Association [Member]
Line of Credit Facility [Line Items]
Line of credit, current maximum borrowing capacity			$ 375,000
Commitment by bank, maximum	$ 750,000
Company loans secured by mortgage loans borrowing base availability maximum percentage	60.00%
Debt instrument covenant related to debt service amount, ratio	1.35
Debt instrument covenant related to debt service coverage amount ratio, maximum	0.50
Maximum [Member] | KeyBank National Association [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument per diem fee rate percentage	0.30%
Maximum [Member] | KeyBank National Association [Member] | Included in the borrowing base for Greater than 30 months [Member]
Line of Credit Facility [Line Items]
Debt instrument covenant related to debt service amount, ratio	1
Maximum [Member] | KeyBank National Association [Member] | Secured by Stabilized Self-Storage Properties [Member]
Line of Credit Facility [Line Items]
Debt instrument covenant related to debt service amount, ratio	1.30
Minimum [Member] | KeyBank National Association [Member]
Line of Credit Facility [Line Items]
Company loans secured by mortgage loans underlying real estate fair value minimum percentage to maximum principal amount borrowed	50.00%
Percentage of total development cost of the non-stabilized self-storage properties	75.00%
Minimum [Member] | KeyBank National Association [Member] | Jernigan Capital Operating Company Limited Liability Company [Member]
Line of Credit Facility [Line Items]
Debt instrument per diem fee rate percentage	0.25%
Minimum [Member] | KeyBank National Association [Member] | Included in the borrowing base for Greater than 18 months [Member]
Line of Credit Facility [Line Items]
Mortgage loans minimal months inclusion in borrowing base period	18 months
Minimum [Member] | KeyBank National Association [Member] | Included in the borrowing base for Greater than 30 months [Member]
Line of Credit Facility [Line Items]
Mortgage loans minimal months inclusion in borrowing base period	30 months
Minimum [Member] | KeyBank National Association [Member] | Secured by Stabilized Self-Storage Properties [Member]
Line of Credit Facility [Line Items]
Company loans secured by self-storage properties underlying real estate fair value minimum percentage to maximum principal amount borrowed	65.00%

DEBT (Term Loans) (Narrative) (

DEBT (Term Loans) (Narrative) (Details) - USD ($) $ in Thousands	Aug. 17, 2018	Sep. 30, 2020	Dec. 31, 2019	Aug. 13, 2019	Jan. 18, 2019
Debt Instrument [Line Items]
Term loans principal amount		$ 40,973	$ 40,791
First Bank Term Loans [Member]
Debt Instrument [Line Items]
Term loans principal amount	$ 24,900			$ 7,100	$ 9,200
Maturity Date	Aug. 1, 2021
Description of variable rate basis	Borrowings under the FirstBank Term Loans bear interest at a floating variable rate of one-month LIBOR plus 2.25%, which is reset monthly.
Term loans, financial covenant	The FirstBank Term Loans contain a financial covenant that requires the Operating Company to maintain a debt service coverage ratio of 1.35 to 1.
Term loans, covenant compliance		As of September 30, 2020, the Company was in compliance with all of its financial covenants of the FirstBank Term Loans
Debt instrument covenant related to debt service coverage amount ratio, maximum		1.35
London Interbank Offered Rate (LIBOR) [Member] | First Bank Term Loans [Member]
Debt Instrument [Line Items]
Effective Interest Rate	2.25%
London Interbank Offered Rate (LIBOR) [Member] | First Bank Term Loans [Member] | Interest Rate Swap 1 to 4 Fixes [Member]
Debt Instrument [Line Items]
Effective Interest Rate		2.2925%
London Interbank Offered Rate (LIBOR) [Member] | First Bank Term Loans [Member] | Interest Rate Swap 5 Fixes [Member]
Debt Instrument [Line Items]
Effective Interest Rate		1.6025%

RISK MANAGEMENT AND USE OF FI_3

RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS (Narrative) (Details) - USD ($) $ in Thousands	1 Months Ended		3 Months Ended			9 Months Ended		12 Months Ended
	May 31, 2020	Mar. 31, 2020	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2020	Dec. 31, 2019
Reclassification to earnings as interest expense			$ (262)	$ 1		$ (501)	$ 5
Amended and Restated Credit Facility
Interest rate Swap/Cap, notional amount			100,000			100,000
Scenario, Forecast [Member]
Reclassification to earnings as interest expense								$ 900
Interest Rate Cap [Member]
Interest rate Swap/Cap, notional amount	$ 100,000	$ 20,000			$ 100,000
Interest rate swap, maturity date	Mar. 24, 2023	Dec. 28, 2021			Dec. 28, 2021
Interest Rate Cap [Member] | Nondesignated [Member]
Net carrying amount of interest rate swap			$ 50			$ 50			$ 10
London Interbank Offered Rate (LIBOR) [Member] | Interest Rate Cap [Member]
Interest rate cap	0.50%	1.50%			2.50%

RISK MANAGEMENT AND USE OF FI_4

RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS (Terms and Fair Values of Derivative Financial Instruments) (Details) - Designated [Member] - Cash Flow [Member] - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Derivative [Line Items]
Notional Amount	$ 141,175	$ 41,175
Fair Value	(1,109)	(393)
Swap One [Member]
Derivative [Line Items]
Notional Amount	$ 9,150	9,150
Strike	2.2925%
Fair Value	$ (165)	(104)
Swap Two [Member]
Derivative [Line Items]
Notional Amount	$ 7,125	7,125
Strike	2.2925%
Fair Value	$ (129)	(81)
Swap Three [Member]
Derivative [Line Items]
Notional Amount	$ 8,625	8,625
Strike	2.2925%
Fair Value	$ (155)	(98)
Swap Four [Member]
Derivative [Line Items]
Notional Amount	$ 9,188	9,188
Strike	2.2925%
Fair Value	$ (165)	(105)
Swap Five [Member]
Derivative [Line Items]
Notional Amount	$ 7,087	7,087
Strike	1.6025%
Fair Value	$ (87)	(5)
Swap Six [Member]
Derivative [Line Items]
Notional Amount	$ 100,000	0
Strike	0.357%
Fair Value	$ (408)	$ 0

RISK MANAGEMENT AND USE OF FI_5

RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS (Effect of Derivatives Designated as Hedging Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification of realized losses (gains) on interest rate swaps	$ 262	$ (1)	$ 501	$ (5)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Reclassification of realized losses (gains) on interest rate swaps	238	(1)	461	(5)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member] | Designated [Member] | Term Loan Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Loss Recognized in OCI on Derivatives	(54)	(58)	(1,152)	(495)
Reclassification of realized losses (gains) on interest rate swaps	$ 238	$ (1)	$ 461	$ (5)

RISK MANAGEMENT AND USE OF FI_6

RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS (Changes in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Beginning Balance			$ 588,874
Other comprehensive income (loss):
Unrealized losses on interest rate swaps	$ (59)	$ (58)	(1,216)	$ (495)
Reclassification of realized losses (gains) on interest rate swaps	262	(1)	501	(5)
Ending Balance	535,351		535,351
Accumulated Other Comprehensive Income (Loss) [Member]
Beginning Balance	(1,268)	(441)	(393)	0
Other comprehensive income (loss):
Ending Balance	(1,084)	(500)	(1,084)	(500)
Accumulated Gain (Loss), Net, Cash Flow Hedge, Parent [Member]
Other comprehensive income (loss):
Unrealized losses on interest rate swaps	(54)	(58)	(1,152)	(495)
Reclassification of realized losses (gains) on interest rate swaps	238	(1)	461	(5)
Other comprehensive income (loss)	$ 184	$ (59)	$ (691)	$ (500)

RISK MANAGEMENT AND USE OF FI_7

RISK MANAGEMENT AND USE OF FINANCIAL INSTRUMENTS (Effect of Derivatives not Designated as Hedging Instruments) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Nondesignated [Member] | Interest Rate Cap [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain (Loss) Recognized in Earnings on Derivative	$ (127)	$ (61)	$ (208)	$ (89)

STOCKHOLDERS' EQUITY (Common St

STOCKHOLDERS' EQUITY (Common Stock Offerings and Repurchase Plan) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended				9 Months Ended		12 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Dec. 18, 2019	Dec. 31, 2018
Common stock, shares issued					23,263,130		22,423,283
Common stock, shares outstanding					23,263,130		22,423,283
Net proceeds from issuance of common stock					$ 15,004	$ 34,645
Retirement of common stock	$ 363	$ 36	$ 396	$ 73
ATM Program [Member]
Net proceeds from issuance of common stock					$ 101,400
Issuance of shares, net of offering costs (in shares)					810,000
Shares issued, price per share					$ 19.07
ATM Program [Member] | Maximum [Member]
Equity offering program, increase in aggregate offering price								$ 100,000
ATM Program [Member] | Since the Start of ATM Program [Member]
Issuance of shares, net of offering costs (in shares)					4,962,535
Shares issued, price per share					$ 21.01
Series A Preferred Stock [Member]
Preferred stock, par value (in dollars per share)					$ 0.01		$ 0.01
Preferred stock, dividend rate					7.00%		7.00%
Preferred stock, shares issued					139,875		133,500
Preferred stock, shares outstanding					139,875		133,500
Series B Preferred Stock [Member]
Preferred stock, par value (in dollars per share)					$ 0.01		$ 0.01
Preferred stock, dividend rate					7.00%		7.00%
Preferred stock, shares issued					1,571,734		1,571,734
Preferred stock, shares outstanding					1,571,734		1,571,734
Series B Preferred Stock [Member] | ATM Program [Member]
Preferred stock, shares issued					71,734
Shares issued, price per share					$ 22.94
Restricted Stock [Member]
Nonvested restricted stock	150,836		208,665		148,961	216,165	216,165		159,165
Share based compensation expense, period for recognition					2 years 1 month 6 days

STOCKHOLDERS' EQUITY (Equity In

STOCKHOLDERS' EQUITY (Equity Incentive Plan and Restricted Stock Awards) (Narrative) (Details) - USD ($) $ in Millions

3 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2020

Sep. 30, 2019

Sep. 30, 2020

Sep. 30, 2019

Dec. 31, 2019

Dec. 31, 2018

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2024

Dec. 31, 2023

Dec. 31, 2022

Dec. 31, 2021

Restricted Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of shares granted

7,500

59,402

145,922

Number of shares forfeited

0

0

1,666

Restricted stock expense, recognized

$ 0.4

$ 0.6

$ 1.9

$ 1.7

Unrecognized share based compensation expense

$ 3

Share based compensation expense, period for recognition

2 years 1 month 6 days

Number of shares, vested

1,875

126,606

87,256

Restricted Stock [Member] | Amended and Restated 2015 Equity Incentive Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of shares granted

568,911

509,509

Restricted Stock Units (RSUs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of shares granted

0

0

31,243

Number of contingently issuable Shares

31,243

Maximum [Member] | Restricted Stock [Member] | Amended and Restated 2015 Equity Incentive Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity award vesting period

5 years

Minimum [Member] | Restricted Stock [Member] | Amended and Restated 2015 Equity Incentive Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Equity award vesting period

3 years

Non Employee Director [Member] | Restricted Stock [Member] | Amended and Restated 2015 Equity Incentive Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of shares forfeited

1,666

1,667

1,667

Number of shares, vested

126,606

87,256

99,503

46,413

55,172

Non Employee Director [Member] | Share-based Compensation Award, Tranche Two [Member] | Scenario, Forecast [Member] | Restricted Stock [Member] | Amended and Restated 2015 Equity Incentive Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of vested or expected to vest, shares

65,501

Non Employee Director [Member] | Share-based Compensation Award, Tranche Three [Member] | Scenario, Forecast [Member] | Restricted Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of vested or expected to vest, shares

63,207

Non Employee Director [Member] | Share-based Compensation Award, Tranche Three [Member] | Scenario, Forecast [Member] | Restricted Stock [Member] | Amended and Restated 2015 Equity Incentive Plan [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of vested or expected to vest, shares

63,207

Non Employee Director [Member] | Share Based Compensation Award Tranche Four [Member] | Scenario, Forecast [Member] | Restricted Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of vested or expected to vest, shares

10,124

Non Employee Director [Member] | Share Based Compensation Award Tranche Five [Member] | Scenario, Forecast [Member] | Restricted Stock [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Number of vested or expected to vest, shares

10,129

STOCKHOLDERS' EQUITY (Preferred

STOCKHOLDERS' EQUITY (Preferred Stock) (Narrative) (Details) - USD ($) $ / shares in Units, $ in Thousands	May 07, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Mar. 29, 2018	Jul. 27, 2016
Class of Stock [Line Items]
Common stock, par value (in dollars per share)		$ 0.01						$ 0.01		$ 0.01
Preferred ATM shares, aggregate maximum offering price											$ 45,000
Stock dividend paid on preferred stock		$ 2,125	$ 2,125	$ 2,125	$ 2,125	$ 2,125	$ 2,125	$ 6,375	$ 6,375
Series A Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares authorized		300,000						300,000		300,000
Preferred stock, shares outstanding		139,875						139,875		133,500
Amount of preferred shares issuable in future												$ 125,000
Preferred stock, par value (in dollars per share)		$ 0.01						$ 0.01		$ 0.01
Preferred stock, liquidation preference per share												$ 1,000
Preferred stock, redemption terms								The Series A Preferred Stock may be redeemed at the Company’s option (i) after five years from the Effective Date at a price equal to 105% of the Liquidation Value per share plus the value of all accumulated and unpaid Cash Distributions and Stock Dividends, and (ii) after six years from the Effective Date at a price equal to 100% of the Liquidation Value per share plus the value of all accumulated and unpaid Cash Distributions and Stock Dividends. In the event of certain change of control events affecting the Company prior to the third anniversary of the Effective Date, the Company must redeem all shares of Series A Preferred Stock for a price equal to (a) the Liquidation Value, plus (b) accumulated and unpaid Cash Distributions and Stock Dividends, plus (c) a make-whole premium designed to provide the holders of the Series A Preferred Stock with a return on the redeemed shares equal to a 14.0% internal rate of return through the third anniversary of the Effective Date.
Preferred stock, dividend rate								7.00%		7.00%
Debt instrument covenant debt to total intangible asset ratio								0.4
Preferred stock, shares issued		139,875						139,875		133,500
Stock dividend paid on preferred stock		$ 2,125	$ 2,125	$ 2,125	$ 2,125	$ 2,125	$ 2,125
Dividend payable, amount per share	$ 17.85
Dividends payable date	Oct. 15, 2020
Dividends payable, date of record	Oct. 1, 2020
Series A Preferred Stock [Member] | Scenario, Plan [Member]
Class of Stock [Line Items]
Percentage of increase in book value								25.00%
Internal rate of return to the preferred shareholders								14.00%
Series A Preferred Stock [Member] | Five Years From the Effective Date [Member]
Class of Stock [Line Items]
Percentage of Preferred stock redemption								105.00%
Series A Preferred Stock [Member] | Six Years From the Effective Date [Member]
Class of Stock [Line Items]
Percentage of Preferred stock redemption								100.00%
Series A Preferred Stock [Member] | Until Sixth Anniversary [Member]
Class of Stock [Line Items]
Preferred stock, dividend rate								7.00%
Series A Preferred Stock [Member] | After Sixth Anniversary [Member]
Class of Stock [Line Items]
Preferred stock, dividend rate								8.50%
Series A Preferred Stock [Member] | After Third Anniversary [Member]
Class of Stock [Line Items]
Internal rate of return to the preferred shareholders								14.00%
Series A Preferred Stock [Member] | Occurrence of certain triggering events [Member]
Class of Stock [Line Items]
Preferred stock, dividend rate								5.00%
Series B Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares authorized		3,750,000						3,750,000		3,750,000
Preferred stock, shares outstanding		1,571,734						1,571,734		1,571,734
Preferred stock, par value (in dollars per share)		$ 0.01						$ 0.01		$ 0.01
Preferred stock, liquidation preference per share		25						$ 25
Preferred stock, redemption terms								On or after January 26, 2023, the Series B Preferred Stock may be redeemed, at the Company’s option, upon not less than 30 nor more than 60 days’ written notice, in whole or in part, at any time and from time to time, for cash at a redemption price equal to $25.00 per share, plus any accrued and unpaid dividends (whether or not authorized or declared) to, but excluding, the date fixed for redemption. Holders of Series B Preferred Stock will have no right to require the redemption or repurchase of the Series B Preferred Stock. Upon the occurrence of a Change of Control (as defined in the articles supplementary designating the terms of the Series B Preferred Stock (the “Series B Articles Supplementary”)), the Company may redeem for cash, in whole or in part, the Series B Preferred Stock within 120 days after the date on which such Change of Control occurred, by paying $25.00 per share, plus any accrued and unpaid dividends (whether or not authorized or declared) to, but excluding, the date fixed for redemption.
Preferred stock redemption price per share		$ 25						$ 25
Preferred stock, dividend rate								7.00%		7.00%
Preferred stock, dividend declared per share								$ 1.7500
Net proceeds (offering costs) from issuance of preferred stock								$ 0	$ (103)
Preferred stock, shares issued		1,571,734						1,571,734		1,571,734
ATM Program [Member]
Class of Stock [Line Items]
Shares issued, price per share		$ 19.07						$ 19.07
ATM Program [Member] | Series B Preferred Stock [Member]
Class of Stock [Line Items]
Net proceeds (offering costs) from issuance of preferred stock								$ 1,300
Preferred stock, shares issued		71,734						71,734
Shares issued, price per share		$ 22.94						$ 22.94

STOCKHOLDERS' EQUITY (Summary o

STOCKHOLDERS' EQUITY (Summary of Changes in Restricted Shares) (Details) - $ / shares	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Restricted Stock [Member]
Class of Stock [Line Items]
Shares, Nonvested shares at beginning of period	150,836	208,665	216,165	159,165	159,165
Shares, Granted		7,500	59,402	145,922
Shares, Vested	(1,875)		(126,606)	(87,256)
Shares, Forfeited	0		0	(1,666)
Shares, Nonvested shares at end of period	148,961	216,165	148,961	216,165	216,165
Weighted average grant date fair value, Nonvested at beginning of period	$ 20.93	$ 20.35	$ 20.34	$ 18.39	$ 18.39
Weighted average grant date fair value, Granted		19.84	18	21.60
Weighted average grant date fair value, Vested	19.84		18.53	18.95
Weighted average grant date fair value, Forfeited	0		0	18.10
Weighted average grant date fair value, Nonvested at end of period	$ 20.94	$ 20.34	$ 20.94	$ 20.34	$ 20.34
Restricted Stock Units (RSUs) [Member]
Class of Stock [Line Items]
Shares, Nonvested shares at beginning of period	31,243	0
Shares, Granted	0	0	31,243
Shares, Nonvested shares at end of period	31,243	0	31,243	0
Weighted average grant date fair value, Nonvested at beginning of period	$ 26	$ 0
Weighted average grant date fair value, Granted	0	0	$ 26
Weighted average grant date fair value, Nonvested at end of period	$ 26	$ 0	$ 26	$ 0
Number of contingently issuable Shares			31,243

EARNINGS PER SHARE (Schedule of

EARNINGS PER SHARE (Schedule of Earnings per Share, Basic and Diluted) (Details) $ / shares in Units, $ in Thousands	3 Months Ended						6 Months Ended	9 Months Ended
	Sep. 30, 2020USD ($)$ / sharesshares	Jun. 30, 2020USD ($)	Mar. 31, 2020USD ($)	Sep. 30, 2019USD ($)$ / sharesshares	Jun. 30, 2019USD ($)	Mar. 31, 2019USD ($)	Jun. 30, 2020USD ($)	Sep. 30, 2020USD ($)$ / sharesshares	Sep. 30, 2019USD ($)$ / sharesshares
Shares Outstanding
Weighted average common shares - basic | shares	23,113,558			22,019,875				23,052,347	21,173,946
Effect of dilutive securities | shares	0			213,719				0	191,293
Weighted average common shares, all classes | shares	23,113,558			22,233,594				23,052,347	21,365,239
Calculation of Earnings per Share - basic
Net income (loss)	$ (5,631)	$ (993)	$ (54,782)	$ 10,954	$ 14,874	$ 12,114		$ (61,407)	$ 37,941
Net income allocated to preferred stockholders	5,309			5,157				15,760	15,283
Less: Net loss attributable to non-controlling interests	1,005			0				3,604	0
Net income (loss) allocated to unvested restricted shares	0			56			$ 0	0	203
Dividends declared on unvested restricted shares	0							92
Net income (loss) attributable to common shareholders, adjusted	$ (9,935)			$ 5,741				$ (73,655)	$ 22,455
Weighted average common shares - basic | shares	23,113,558			22,019,875				23,052,347	21,173,946
Earnings (loss) per share - basic | $ / shares	$ (0.43)			$ 0.26				$ (3.20)	$ 1.06
Calculation of Earnings per Share - diluted
Net income (loss)	$ (5,631)	$ (993)	$ (54,782)	$ 10,954	$ 14,874	$ 12,114		$ (61,407)	$ 37,941
Net income allocated to preferred stockholders	5,309			5,157				15,760	15,283
Net loss attributable to non-controlling interest	(1,005)			0				(3,604)	0
Dividends declared on unvested restricted shares	0							92
Net income attributable to common shareholders, adjusted	$ (9,935)			$ 5,797				$ (73,655)	$ 22,658
Weighted average common shares - diluted | shares	23,113,558			22,233,594				23,052,347	21,365,239
Earnings (loss) per share - diluted | $ / shares	$ (0.43)			$ 0.26				$ (3.20)	$ 1.06
Unvested restricted shares of common stock participation ratio in dividends with unrestricted shares of common								1
Operating Company Units [Member]
Calculation of Earnings per Share - diluted
Number of shares excluded from the calculation of diluted shares | shares	2,354,407							1,699,478
Restricted Stock [Member]
Calculation of Earnings per Share - diluted
Number of shares excluded from the calculation of diluted shares | shares	149,572							193,654

RELATED PARTY TRANSACTIONS (Nar

RELATED PARTY TRANSACTIONS (Narrative) (Details) - USD ($) $ in Thousands	Feb. 20, 2020	Feb. 20, 2020	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Related Party Transaction [Line Items]
Fair value of investments			$ 316,254		$ 316,254		$ 549,684
Base management fee, annual rate		1.50%
Percentage of base management fee			0.375%		0.375%
Base management fees	$ 1,200			$ 2,100		$ 6,200
Fees to Manager			$ 0	2,131	$ 1,230	6,203
Due to Manager			0		$ 0		3,164
Management fee, description					The Manager computed the base management fee within 30 days after the end of the fiscal quarter with respect to which such installment is payable and promptly delivered such calculation to the Company’s Board of Directors. The amount of the installment shown in the calculation is due and payable no later than the date which is five business days after the date of delivery of such computation to the Board of Directors
Incentive fee, description					Notwithstanding application of the incentive fee formula, any incentive fee earned shall not be paid with respect to any fiscal quarter unless cumulative annual stockholder total return for the four most recently completed fiscal quarters is greater than 8%. Any computed incentive fee earned but not paid because of the foregoing hurdle will accrue until such 8% cumulative annual stockholder total return is achieved
Expenses reimbursable to Manager	400			1,100		3,100
Investment in and advances to self-storage real estate venture			4,053		$ 4,053		11,247
Interest income from investments			5,553	10,216	20,117	27,578
Income (loss) from equity method investments			(2,041)	165	(2,195)	407
Incentive fee earned by the Manager	$ 0			0		0
SL1 Venture [Member]
Related Party Transaction [Line Items]
Investment in and advances to self-storage real estate venture			4,100		4,100		11,200
Income (loss) from equity method investments			(2,000)	200	(2,200)	400
Equity Method Investments [Member]
Related Party Transaction [Line Items]
Fair value of investments			316,300		316,300		$ 549,700
Interest income from investments			$ (9,500)		$ 18,300
Income (loss) from equity method investments				$ 16,500		$ 47,200

SUBSEQUENT EVENTS (Merger Agree

SUBSEQUENT EVENTS (Merger Agreement) (Narrative) (Details) - Subsequent Event [Member] $ in Millions	Nov. 06, 2020USD ($)	Oct. 31, 2020facility
Subsequent Event [Line Items]
Number of facilities | facility		43
Prepayment penalty	$ 0
Term Loans [Member]
Subsequent Event [Line Items]
Repayment of debt	41.2
Class A Membership Units [Member] | Development Property Investments [Member] | New York City 4, New York City 5 and Orlando 5 [Member] | Limited Liability Company that Owned the Property [Member] | Loan Investments [Member]
Subsequent Event [Line Items]
Minority interest, ownership percentage		100.00%
Secured revolving credit facility [Member]
Subsequent Event [Line Items]
Repayment of debt	242.6
Interest Rate Contract [Member]
Subsequent Event [Line Items]
Loss on termination of interest rate contract	1.1
Restricted Stock [Member]
Subsequent Event [Line Items]
Amount received in respect of previously unvested awards	2.6
Long-Term Incentive Plan Units [Member]
Subsequent Event [Line Items]
Amount received in respect of previously unvested awards	$ 1