Investment in Joint Ventures - Summary of Company's Unconsolidated Joint Ventures (Detail) $ in Millions	3 Months Ended
Mar. 31, 2021 USD ($) Property	Dec. 31, 2020 USD ($)
Sovran HHF Storage Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Properties \| Property	36
Company common ownership interest	20.00%
Carrying value of investment	$ 60.0	$ 60.5
Sovran HHF Storage Holdings II LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Properties \| Property	22
Company common ownership interest	15.00%
Carrying value of investment	$ 27.0	27.3
Life Storage-SERS Storage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Properties \| Property	3
Company common ownership interest	20.00%
Carrying value of investment	$ 3.0	3.0
Life Storage-HIERS Storage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Properties \| Property	17
Company common ownership interest	20.00%
Carrying value of investment	$ 14.2	14.3
Iskalo Office Holdings, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Company common ownership interest	49.00%
Carrying value of investment	$ (2.5)	(2.5)
Life Storage Spacemax, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Properties \| Property	6
Company common ownership interest	40.00%
Carrying value of investment	$ 16.5	16.7
Life Storage Virtus, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Number of Properties \| Property	1
Company common ownership interest	20.00%
Carrying value of investment	$ 1.4	1.5
SNL Orix Merrick, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Company common ownership interest	5.00%
Carrying value of investment		2.5
Joint Ventures with Properties in Development Stage [Member]
Schedule of Equity Method Investments [Line Items]
Number of Properties \| Property	7
Company common ownership interest	Various
Carrying value of investment	$ 11.5	10.4
Other Unconsolidated Joint Ventures [Member]
Schedule of Equity Method Investments [Line Items]
Number of Properties \| Property	6
Company common ownership interest	Various
Carrying value of investment	$ 6.8	$ 6.8

Equity method investment ownership description.

No definition available.

Name:	lsi_EquityMethodInvestmentOwnershipDescription
Namespace Prefix:	lsi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=109237563&loc=d3e33749-111570

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 25
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=120311839&loc=d3e8813-108599

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_EquityMethodInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The number of real estate properties owned as of the balance sheet date.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfRealEstateProperties
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_SovranHHFStorageHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_SovranHHFStorageHoldingsIILLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_LifeStorageSERSStorageLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_LifeStorageHIERSStorageLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_IskaloOfficeHoldingsLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_LifeStorageSpacemaxLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_LifeStorageVirtusLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_SNLOrixMerrickLLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_JointVenturesWithPropertiesInDevelopmentStageMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=lsi_OtherUnconsolidatedJointVentureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: