Investment in Storage Facilities and Intangible Assets - Schedule of Purchase Price of Facilities Acquired (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2022 USD ($) Property	Sep. 30, 2021 Property
Investment Holdings [Line Items]
Number of Properties | Property	43	62
Purchase Price	$ 860,638
Consideration paid, Cash Paid	811,628
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	35,101
Consideration paid, Value of Operating Partnership Units Issued	10,300
Consideration paid, Net Other Liabilities (Assets) Assumed	3,609
Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	106,469
Acquisition Date Fair Value, In-Place Customer Leases	8,845
Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 745,324
CA [Member] | Asset Acquired on 1/4/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	6
Date of Acquisition	Jan. 04, 2022
Purchase Price	$ 165,225
Consideration paid, Cash Paid	165,160
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	65
Acquisition Date Fair Value, In-Place Customer Leases	1,661
CA [Member] | Asset Acquired on 1/4/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	20,321
CA [Member] | Asset Acquired on 1/4/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 143,243
CA [Member] | Asset Acquired on 6/21/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Jun. 21, 2022
Purchase Price	$ 12,675
Consideration paid, Cash Paid	12,641
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	34
Acquisition Date Fair Value, In-Place Customer Leases	136
CA [Member] | Asset Acquired on 6/21/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	5,967
CA [Member] | Asset Acquired on 6/21/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 6,572
CA [Member] | Asset Acquired On 8/23/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Aug. 23, 2022
Purchase Price	$ 10,709
Consideration paid, Cash Paid	10,690
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	19
Acquisition Date Fair Value, In-Place Customer Leases	93
CA [Member] | Asset Acquired On 8/23/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	1,324
CA [Member] | Asset Acquired On 8/23/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 9,292
GA, NC, SC [Member] | Asset Acquired on 3/11/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	3
Date of Acquisition	Mar. 11, 2022
Purchase Price	$ 48,586
Consideration paid, Cash Paid	48,446
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	140
Acquisition Date Fair Value, In-Place Customer Leases	360
GA, NC, SC [Member] | Asset Acquired on 3/11/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	3,926
GA, NC, SC [Member] | Asset Acquired on 3/11/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 44,300
IL, NC, TX [Member] | Asset Acquired on 3/15/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	8
Date of Acquisition	Mar. 15, 2022
Purchase Price	$ 116,048
Consideration paid, Cash Paid	115,410
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	638
Acquisition Date Fair Value, In-Place Customer Leases	1,317
IL, NC, TX [Member] | Asset Acquired on 3/15/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	12,292
IL, NC, TX [Member] | Asset Acquired on 3/15/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 102,439
MD [Member] | Asset Acquired on 3/28/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Mar. 28, 2022
Purchase Price	$ 21,651
Consideration paid, Cash Paid	21,646
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	5
Acquisition Date Fair Value, In-Place Customer Leases	155
MD [Member] | Asset Acquired on 3/28/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	1,640
MD [Member] | Asset Acquired on 3/28/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 19,856
NY [Member] | Asset Acquired on 4/4/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Apr. 04, 2022
Purchase Price	$ 35,802
Consideration paid, Cash Paid	5,557
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	30,186
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	59
Acquisition Date Fair Value, In-Place Customer Leases	235
NY [Member] | Asset Acquired on 4/4/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	10,287
NY [Member] | Asset Acquired on 4/4/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 25,280
NY [Member] | Asset Acquired on 5/17/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	2
Date of Acquisition	May 17, 2022
Purchase Price	$ 32,487
Consideration paid, Cash Paid	32,374
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	113
Acquisition Date Fair Value, In-Place Customer Leases	369
NY [Member] | Asset Acquired on 5/17/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	1,524
NY [Member] | Asset Acquired on 5/17/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 30,594
NY [Member] | Asset Acquired On 8/12/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Aug. 12, 2022
Purchase Price	$ 29,000
Consideration paid, Cash Paid	24,130
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	4,915
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	(45)
Acquisition Date Fair Value, In-Place Customer Leases	187
NY [Member] | Asset Acquired On 8/12/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	8,079
NY [Member] | Asset Acquired On 8/12/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 20,734
FL [Member] | Asset Acquired on 4/19/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	3
Date of Acquisition	Apr. 19, 2022
Purchase Price	$ 52,343
Consideration paid, Cash Paid	52,060
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	283
Acquisition Date Fair Value, In-Place Customer Leases	635
FL [Member] | Asset Acquired on 4/19/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	7,894
FL [Member] | Asset Acquired on 4/19/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 43,814
FL [Member] | Asset Acquired on 5/10/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	May 10, 2022
Purchase Price	$ 17,218
Consideration paid, Cash Paid	17,112
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	106
Acquisition Date Fair Value, In-Place Customer Leases	200
FL [Member] | Asset Acquired on 5/10/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	3,712
FL [Member] | Asset Acquired on 5/10/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 13,306
FL [Member] | Asset Acquired on 5/12/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	May 12, 2022
Purchase Price	$ 36,452
Consideration paid, Cash Paid	36,254
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	198
Acquisition Date Fair Value, In-Place Customer Leases	272
FL [Member] | Asset Acquired on 5/12/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	5,101
FL [Member] | Asset Acquired on 5/12/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 31,079
FL [Member] | Asset Acquired on 5/31/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	May 31, 2022
Purchase Price	$ 22,021
Consideration paid, Cash Paid	21,880
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	141
Acquisition Date Fair Value, In-Place Customer Leases	287
FL [Member] | Asset Acquired on 5/31/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	3,563
FL [Member] | Asset Acquired on 5/31/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 18,171
FL [Member] | Asset Acquired On 9/22/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Sep. 22, 2022
Purchase Price	$ 17,363
Consideration paid, Cash Paid	17,233
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	130
Acquisition Date Fair Value, In-Place Customer Leases	164
FL [Member] | Asset Acquired On 9/22/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	1,830
FL [Member] | Asset Acquired On 9/22/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 15,369
GA [Member] | Asset Acquired on 4/22/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Apr. 22, 2022
Purchase Price	$ 16,403
Consideration paid, Cash Paid	16,390
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	13
Acquisition Date Fair Value, In-Place Customer Leases	167
GA [Member] | Asset Acquired on 4/22/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	1,333
GA [Member] | Asset Acquired on 4/22/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 14,903
MA [Member] | Asset Acquired on 4/25/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Apr. 25, 2022
Purchase Price	$ 20,083
Consideration paid, Cash Paid	20,087
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	(4)
Acquisition Date Fair Value, In-Place Customer Leases	232
MA [Member] | Asset Acquired on 4/25/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	810
MA [Member] | Asset Acquired on 4/25/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 19,041
MA [Member] | Asset Acquired On 9/21/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Sep. 21, 2022
Purchase Price	$ 16,650
Consideration paid, Cash Paid	16,618
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	32
Acquisition Date Fair Value, In-Place Customer Leases	191
MA [Member] | Asset Acquired On 9/21/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	640
MA [Member] | Asset Acquired On 9/21/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 15,819
TX [Member] | Asset Acquired on 5/17/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	May 17, 2022
Purchase Price	$ 17,097
Consideration paid, Cash Paid	6,608
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	10,300
Consideration paid, Net Other Liabilities (Assets) Assumed	189
Acquisition Date Fair Value, In-Place Customer Leases	209
TX [Member] | Asset Acquired on 5/17/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	1,273
TX [Member] | Asset Acquired on 5/17/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 15,615
NC [Member] | Asset Acquired On 7/6/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Jul. 06, 2022
Purchase Price	$ 20,059
Consideration paid, Cash Paid	19,970
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	89
Acquisition Date Fair Value, In-Place Customer Leases	203
NC [Member] | Asset Acquired On 7/6/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	428
NC [Member] | Asset Acquired On 7/6/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 19,428
NV [Member] | Asset Acquired On 8/12/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Aug. 12, 2022
Purchase Price	$ 29,113
Consideration paid, Cash Paid	29,154
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	(41)
Acquisition Date Fair Value, In-Place Customer Leases	247
NV [Member] | Asset Acquired On 8/12/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	2,354
NV [Member] | Asset Acquired On 8/12/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 26,512
AZ [Member] | Asset Acquired On 8/24/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	1
Date of Acquisition	Aug. 24, 2022
Purchase Price	$ 30,550
Consideration paid, Cash Paid	30,388
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	162
Acquisition Date Fair Value, In-Place Customer Leases	336
AZ [Member] | Asset Acquired On 8/24/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	3,959
AZ [Member] | Asset Acquired On 8/24/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 26,255
MO [Member] | Asset Acquired On 9/14/2022 [Member]
Investment Holdings [Line Items]
Number of Properties | Property	5
Date of Acquisition	Sep. 14, 2022
Purchase Price	$ 93,103
Consideration paid, Cash Paid	91,820
Consideration Paid, Carrying Value of Noncontrolling Interest in Joint Venture	0
Consideration paid, Value of Operating Partnership Units Issued	0
Consideration paid, Net Other Liabilities (Assets) Assumed	1,283
Acquisition Date Fair Value, In-Place Customer Leases	1,189
MO [Member] | Asset Acquired On 9/14/2022 [Member] | Land [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, Fixed Assets	8,212
MO [Member] | Asset Acquired On 9/14/2022 [Member] | Building, Equipment and Improvements [Member]
Investment Holdings [Line Items]
Acquisition Date Fair Value, In-Place Customer Leases	$ 83,702