Investment in Joint Ventures - Summary of Company's Unconsolidated Joint Ventures (Parenthetical) (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2019 USD ($) Property	Sep. 30, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Distributions from unconsolidated joint ventures	$ 7,419	$ 6,276
Number of storage facilities acquired | Property	28
Sovran HHF Storage Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	$ 219,200
Distributions from unconsolidated joint ventures	4,800
Excess of investment over net asset due to capitalization of acquisition related costs	$ 1,700
Sovran HHF Storage Holdings LLC [Member] | Arizona [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	11
Sovran HHF Storage Holdings LLC [Member] | Colorado [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	4
Sovran HHF Storage Holdings LLC [Member] | Florida [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	3
Sovran HHF Storage Holdings LLC [Member] | Georgia [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	1
Sovran HHF Storage Holdings LLC [Member] | Kentucky [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	2
Sovran HHF Storage Holdings LLC [Member] | Nevada [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	5
Sovran HHF Storage Holdings LLC [Member] | New Jersey [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	2
Sovran HHF Storage Holdings LLC [Member] | Ohio [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	6
Sovran HHF Storage Holdings LLC [Member] | Pennsylvania [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	1
Sovran HHF Storage Holdings LLC [Member] | Tennessee [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	2
Sovran HHF Storage Holdings LLC [Member] | Texas [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	20
Sovran HHF Storage Holdings II LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	$ 87,100
Distributions from unconsolidated joint ventures	1,600
Contribution of company to joint venture as share in capital	$ 300
Sovran HHF Storage Holdings II LLC [Member] | New Jersey [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	17
Sovran HHF Storage Holdings II LLC [Member] | Pennsylvania [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	3
Sovran HHF Storage Holdings II LLC [Member] | Texas [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	10
191 III Life Storage Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Distributions from unconsolidated joint ventures	$ 400
Contribution of company to joint venture as share in capital	100
191 III Life Storage Holdings LLC [Member] | California [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	$ 57,200
191 III Life Storage Holdings LLC [Member] | California [Member] | Storage Facilities [Member]
Schedule of Equity Method Investments [Line Items]
Number of storage facilities acquired | Property	6
Life Storage-SERS Storage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Distributions from unconsolidated joint ventures	$ 100
Life Storage-SERS Storage LLC [Member] | Georgia [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	$ 22,000
Life Storage-SERS Storage LLC [Member] | Georgia [Member] | Storage Facilities [Member]
Schedule of Equity Method Investments [Line Items]
Number of storage facilities acquired | Property	3
Life Storage-HIERS Storage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	$ 45,400
Distributions from unconsolidated joint ventures	300
Contribution of company to joint venture as share in capital	$ 100
Life Storage-HIERS Storage LLC [Member] | Arizona [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	2
Life Storage-HIERS Storage LLC [Member] | Florida [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	1
Life Storage-HIERS Storage LLC [Member] | Texas [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	7
Life Storage-HIERS Storage LLC [Member] | North Carolina [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	1
Life Storage-HIERS Storage LLC [Member] | VIRGINIA
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	1
Iskalo Office Holdings, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Distributions from unconsolidated joint ventures	$ 100
Rent paid during the period	900	$ 900
Urban Box Coralway Storage, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	7,000
SNL/Orix 1200 McDonald Ave., LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	$ 11,900
SNL/Orix 1200 McDonald Ave., LLC [Member] | New York [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	1
SNL Orix Merrick, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	$ 12,500
SNL Orix Merrick, LLC [Member] | New York [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	1
N 32nd Street Self Storage, LLC [Member] | Arizona [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	1
Non-recourse mortgage loan principal outstanding	$ 6,300
Bluebird Sanford Storage LP [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	3,200
Bluebird Sanford Storage LP [Member] | Common Stock Shares [Member]
Schedule of Equity Method Investments [Line Items]
Contribution of company to joint venture as share in capital	300
Bluebird Ingram Storage LP [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding	17,700
Bluebird Ingram Storage LP [Member] | Common Stock Shares [Member]
Schedule of Equity Method Investments [Line Items]
Contribution of company to joint venture as share in capital	1,300
Life Storage Spacemax, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Distributions from unconsolidated joint ventures	100
Life Storage Spacemax, LLC [Member] | Common Stock Shares [Member]
Schedule of Equity Method Investments [Line Items]
Contribution of company to joint venture as share in capital	$ 16,500
Life Storage Spacemax, LLC [Member] | Georgia [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities | Property	6
Non-recourse mortgage loan principal outstanding	$ 42,000
Joint Ventures with Properties in Development Stage [Member]
Schedule of Equity Method Investments [Line Items]
Number Of joint ventures | Property	4
Joint Ventures with Properties in Development Stage [Member] | Common Stock Shares [Member]
Schedule of Equity Method Investments [Line Items]
Contribution of company to joint venture as share in capital	$ 600