Investment in Joint Ventures - Summary of Company's Unconsolidated Joint Ventures (Parenthetical) (Detail) $ in Thousands	6 Months Ended
	Jun. 30, 2019 USD ($) Property	Jun. 30, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Distributions from unconsolidated joint ventures | $	$ 4,865	$ 4,103
Number of storage facilities acquired	6
Sovran HHF Storage Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding | $	$ 219,400
Distributions from unconsolidated joint ventures | $	3,200
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	11
Sovran HHF Storage Holdings LLC [Member] | Colorado [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	4
Sovran HHF Storage Holdings LLC [Member] | Florida [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	3
Sovran HHF Storage Holdings LLC [Member] | Georgia [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	1
Sovran HHF Storage Holdings LLC [Member] | Kentucky [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	2
Sovran HHF Storage Holdings LLC [Member] | Nevada [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	5
Sovran HHF Storage Holdings LLC [Member] | New Jersey [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	2
Sovran HHF Storage Holdings LLC [Member] | Ohio [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	6
Sovran HHF Storage Holdings LLC [Member] | Pennsylvania [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	1
Sovran HHF Storage Holdings LLC [Member] | Tennessee [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	2
Sovran HHF Storage Holdings LLC [Member] | Texas [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	20
Sovran HHF Storage Holdings II LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding | $	$ 87,500
Distributions from unconsolidated joint ventures | $	$ 1,000
Sovran HHF Storage Holdings II LLC [Member] | New Jersey [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	17
Sovran HHF Storage Holdings II LLC [Member] | Pennsylvania [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	3
Sovran HHF Storage Holdings II LLC [Member] | Texas [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	10
191 III Life Storage Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Distributions from unconsolidated joint ventures | $	$ 200
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	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	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 | $	$ 200
Life Storage-HIERS Storage LLC [Member] | Arizona [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	2
Life Storage-HIERS Storage LLC [Member] | Florida [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	1
Life Storage-HIERS Storage LLC [Member] | Texas [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	7
Life Storage-HIERS Storage LLC [Member] | North Carolina [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	1
Life Storage-HIERS Storage LLC [Member] | VIRGINIA
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	1
Iskalo Office Holdings, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Distributions from unconsolidated joint ventures | $	$ 100
Rent paid during the period | $	600	$ 600
Urban Box Coralway Storage, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding | $	6,800
SNL/Orix 1200 McDonald Ave., LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding | $	$ 11,800
SNL/Orix 1200 McDonald Ave., LLC [Member] | New York [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	1
SNL Orix Merrick, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding | $	$ 12,200
SNL Orix Merrick, LLC [Member] | New York [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	1
N 32nd Street Self Storage, LLC [Member] | Arizona [Member]
Schedule of Equity Method Investments [Line Items]
Number of self-storage facilities	1
Non-recourse mortgage loan principal outstanding | $	$ 6,300
NYX Don Mills Storage LP [Member] | Common Stock Shares [Member]
Schedule of Equity Method Investments [Line Items]
Contribution of company to joint venture as share in capital | $	100
Bluebird Sanford Storage LP [Member]
Schedule of Equity Method Investments [Line Items]
Non-recourse mortgage loan principal outstanding | $	3,300
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 | $	17,900
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