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Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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The aggregate costs related to construction and development services during the reporting period.

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The current amount of expenditures for a real estate project that has not yet been completed.

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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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Percentage of the Variable Interest Entity's (VIE) voting interest owned by (or beneficial interest in) the reporting entity (directly or indirectly).

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INVESTMENT ACTIVITY (Details) $ in Thousands					3 Months Ended			12 Months Ended	15 Months Ended	21 Months Ended
INVESTMENT ACTIVITY (Details) $ in Thousands	Aug. 12, 2016 USD ($)	Apr. 18, 2016 USD ($) shares	Apr. 05, 2016 USD ($)	May 14, 2015 USD ($) shares	Mar. 31, 2017 USD ($) property facility	Dec. 31, 2016 USD ($) property	Jun. 30, 2016 USD ($) shares	Dec. 31, 2016 USD ($) item facility	Mar. 31, 2017 USD ($) facility	Sep. 30, 2016 property
Self-storage facilities
Storage facilities					$ 4,020,366	$ 3,998,180		$ 3,998,180	$ 4,020,366
Restricted cash					6,556	7,893		$ 7,893	$ 6,556
OP units issued (in shares) \| shares		61,224		20,408
Issuance of OP Shares		$ 1,500		$ 500
Self storage in operation
Self-storage facilities
Number of self-storage facilities \| facility									3
Total Construction Costs									$ 73,700
Self storage under construction \| PSI
Self-storage facilities
Development costs					195,100				$ 195,100
Expected construction cost					$ 321,100
Number of facilities under contract \| facility					6
Self-storage facilities located in New York
Self-storage facilities
Ownership interest held by the entity (as a percent)								51.00%
Number of joint ventures \| item								2
Self-storage Facility in Washington DC \| PSI
Self-storage facilities
OP units issued (in shares) \| shares							61,224
Issuance of OP Shares							$ 1,500
Self-storage Facility In North Palm Beach, FL
Self-storage facilities
Number of self-storage facilities \| facility									1
Ownership interest held by the entity (as a percent)									100.00%
Total Construction Costs									$ 9,700
Self-storage Facility in Queens, NY
Self-storage facilities
Number of self-storage facilities \| facility									1
Ownership interest held by the entity (as a percent)									100.00%
Total Construction Costs									$ 31,800
Minority ownership interest (as a percent)			49.00%
Amount of net proceeds applied to acquisitions closed during the year			$ 12,500
Self-storage Facility in Bronx, NY
Self-storage facilities
Number of self-storage facilities \| facility									1
Ownership interest held by the entity (as a percent)									100.00%
Total Construction Costs									$ 32,200
Minority ownership interest (as a percent)	49.00%
Amount of net proceeds applied to acquisitions closed during the year	$ 17,000
2017 Acquisitions
Self-storage facilities
Number of self-storage facilities acquired \| property					0
2016 Acquisitions
Self-storage facilities
Number of self-storage facilities acquired \| facility								28
Aggregate purchase price								$ 403,550
2016 Acquisitions \| Self storage under construction
Self-storage facilities
Number of facilities under contract \| facility								3
2016 Acquisitions \| Self-storage facilities located in US
Self-storage facilities
Number of self-storage facilities \| facility								28
Aggregate purchase price								$ 403,600
Intangible value of the in-place leases						18,800		$ 18,800
Estimated life								12 months
Amortization expense					$ 3,900
Number of properties, assumed mortgage \| facility								1
Assumed mortgage debt, at fair value						6,500		$ 6,500
Outstanding principal balance of mortgage debt assumed on acquisitions						6,300		6,300
Premium on debt assumed on acquisitions						$ 200		$ 200
Real Estate Acquisition Expected in 2017
Self-storage facilities
Deposit					$ 1,800				1,800
Number of facilities under contract \| facility					4
Expected aggregate purchase or sales price					$ 61,100				$ 61,100
Self-storage facilities
Self-storage facilities
Number of self-storage facilities acquired \| property						28				28
Aggregate purchase price						$ 403,600
New York \| Self storage under construction \| PSI
Self-storage facilities
Number of facilities under contract \| facility					5
Massachusetts \| Self storage under construction \| PSI
Self-storage facilities
Number of facilities under contract \| facility					1