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Agreement Metric, Capital Distribution Percentage to Third Party

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Agreement Metric, Internal Rate of Return

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Agreement Metric, Return Multiple

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Issuance of debt, aggregate loan proceeds.

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Joint venture agreement percentage of priority distribution, percentage of committed principal amount.

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Total number of investments held by the company.

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Maturity date of mortgage loan within investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, in CCYY-MM-DD format.

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Percentage points added to the reference rate to compute the variable rate on the debt instrument.

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Fixed interest rate related to the interest rate derivative.

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Amount of decrease in the fair value of derivatives recognized in the income statement.

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Date the derivative contract matures, in CCYY-MM-DD format.

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Nominal or face amount used to calculate payment on derivative.

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This element represents the aggregate cost of investments accounted for under the equity method of accounting.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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The amount of assets reported by an equity method investment of the entity.

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For investments which are quantified by principal amount, the principle balance held at close of period.

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Fair value portion of investments in an entity not consolidated. Includes, but is not limited to, investments in an entity that is affiliated with the reporting entity by means of direct or indirect ownership, an entity in which the reporting entity shares control of the entity with another party or group, an entity which the company has significant influence, but does not have control and subsidiaries that are not required to be consolidated and are accounted for using the equity or cost method.

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Amount, after allowance for credit loss, of financing receivable. Excludes financing receivable covered under loss sharing agreement.

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Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

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Amount of other expense (income) that is infrequent in occurrence or unusual in nature.

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The cash outflow associated with the investment in or advances to an entity in which the reporting entity shares control of the entity with another party or group.

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The cash inflow during the period from additional borrowings in aggregate debt. Includes proceeds from short-term and long-term debt.

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The cash inflow from the sale of real estate held-for-investment and real estate joint ventures.

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INVESTMENT IN SELF-STORAGE REAL ESTATE VENTURE (Narrative) (Details) $ in Thousands						1 Months Ended	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2020 USD ($) property	Mar. 04, 2020 USD ($)	Jan. 31, 2020 USD ($)	Sep. 17, 2019 USD ($)	Feb. 27, 2019 USD ($)	Apr. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2020 USD ($) property	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) property	Dec. 31, 2016 USD ($)	Jun. 24, 2020 USD ($)	Jun. 23, 2020	Nov. 07, 2019 USD ($)	Nov. 06, 2019	Jan. 28, 2019 USD ($)	Jan. 27, 2019	Mar. 31, 2016 USD ($)	Mar. 07, 2016 USD ($)
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. 01, 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%