Schedule III - Real Estate and Accumulated Depreciation - Property Summary (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) store
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	985
Debt	$ 1,323,509
Land Initial Cost	2,150,637
Building and Improvements Initial Cost	7,437,285
Adjustments and Costs to Land and Building Subsequent to Acquisition	1,114,477
Gross carrying amount - Land	2,151,319
Gross carrying amount - Building and improvements	8,551,080
Gross carrying amount - Total	10,702,399
Accumulated Depreciation	$ 1,867,750
Self storage facilities | AL
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	8
Debt	$ 5,261
Land Initial Cost	11,021
Building and Improvements Initial Cost	62,772
Adjustments and Costs to Land and Building Subsequent to Acquisition	3,712
Gross carrying amount - Land	11,021
Gross carrying amount - Building and improvements	66,484
Gross carrying amount - Total	77,505
Accumulated Depreciation	$ 10,573
Self storage facilities | AZ
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	23
Debt	$ 22,469
Land Initial Cost	27,535
Building and Improvements Initial Cost	117,304
Adjustments and Costs to Land and Building Subsequent to Acquisition	11,820
Gross carrying amount - Land	27,533
Gross carrying amount - Building and improvements	129,126
Gross carrying amount - Total	156,659
Accumulated Depreciation	$ 31,818
Self storage facilities | CA
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	173
Debt	$ 369,493
Land Initial Cost	646,278
Building and Improvements Initial Cost	1,365,639
Adjustments and Costs to Land and Building Subsequent to Acquisition	160,072
Gross carrying amount - Land	646,728
Gross carrying amount - Building and improvements	1,525,261
Gross carrying amount - Total	2,171,989
Accumulated Depreciation	$ 333,516
Self storage facilities | CO
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	17
Debt	$ 28,776
Land Initial Cost	17,224
Building and Improvements Initial Cost	81,144
Adjustments and Costs to Land and Building Subsequent to Acquisition	17,834
Gross carrying amount - Land	17,942
Gross carrying amount - Building and improvements	98,260
Gross carrying amount - Total	116,202
Accumulated Depreciation	$ 25,649
Self storage facilities | CT
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	6
Debt	$ 6,811
Land Initial Cost	8,598
Building and Improvements Initial Cost	46,974
Adjustments and Costs to Land and Building Subsequent to Acquisition	5,211
Gross carrying amount - Land	8,598
Gross carrying amount - Building and improvements	52,185
Gross carrying amount - Total	60,783
Accumulated Depreciation	$ 11,055
Self storage facilities | FL
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	105
Debt	$ 173,529
Land Initial Cost	186,083
Building and Improvements Initial Cost	799,941
Adjustments and Costs to Land and Building Subsequent to Acquisition	63,289
Gross carrying amount - Land	186,209
Gross carrying amount - Building and improvements	863,104
Gross carrying amount - Total	1,049,313
Accumulated Depreciation	$ 163,231
Self storage facilities | GA
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	71
Debt	$ 68,819
Land Initial Cost	98,519
Building and Improvements Initial Cost	529,048
Adjustments and Costs to Land and Building Subsequent to Acquisition	37,329
Gross carrying amount - Land	98,503
Gross carrying amount - Building and improvements	566,393
Gross carrying amount - Total	664,896
Accumulated Depreciation	$ 86,525
Self storage facilities | HI
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	13
Debt	$ 0
Land Initial Cost	17,663
Building and Improvements Initial Cost	133,870
Adjustments and Costs to Land and Building Subsequent to Acquisition	12,984
Gross carrying amount - Land	17,663
Gross carrying amount - Building and improvements	146,854
Gross carrying amount - Total	164,517
Accumulated Depreciation	$ 33,733
Self storage facilities | IL
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	37
Debt	$ 23,283
Land Initial Cost	49,304
Building and Improvements Initial Cost	247,958
Adjustments and Costs to Land and Building Subsequent to Acquisition	34,806
Gross carrying amount - Land	48,757
Gross carrying amount - Building and improvements	283,311
Gross carrying amount - Total	332,068
Accumulated Depreciation	$ 52,591
Self storage facilities | IN
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	14
Debt	$ 0
Land Initial Cost	12,652
Building and Improvements Initial Cost	60,605
Adjustments and Costs to Land and Building Subsequent to Acquisition	7,255
Gross carrying amount - Land	12,652
Gross carrying amount - Building and improvements	67,860
Gross carrying amount - Total	80,512
Accumulated Depreciation	$ 14,639
Self storage facilities | KS
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	1
Debt	$ 0
Land Initial Cost	366
Building and Improvements Initial Cost	1,897
Adjustments and Costs to Land and Building Subsequent to Acquisition	1,102
Gross carrying amount - Land	366
Gross carrying amount - Building and improvements	2,999
Gross carrying amount - Total	3,365
Accumulated Depreciation	$ 1,326
Self storage facilities | KY
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	10
Debt	$ 30,996
Land Initial Cost	5,670
Building and Improvements Initial Cost	60,442
Adjustments and Costs to Land and Building Subsequent to Acquisition	18,768
Gross carrying amount - Land	6,442
Gross carrying amount - Building and improvements	78,438
Gross carrying amount - Total	84,880
Accumulated Depreciation	$ 16,198
Self storage facilities | LA
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	4
Debt	$ 0
Land Initial Cost	9,105
Building and Improvements Initial Cost	34,923
Adjustments and Costs to Land and Building Subsequent to Acquisition	5,082
Gross carrying amount - Land	9,106
Gross carrying amount - Building and improvements	40,004
Gross carrying amount - Total	49,110
Accumulated Depreciation	$ 5,130
Self storage facilities | MA
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	46
Debt	$ 32,251
Land Initial Cost	73,544
Building and Improvements Initial Cost	270,243
Adjustments and Costs to Land and Building Subsequent to Acquisition	57,334
Gross carrying amount - Land	73,725
Gross carrying amount - Building and improvements	327,396
Gross carrying amount - Total	401,121
Accumulated Depreciation	$ 100,242
Self storage facilities | MD
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	34
Debt	$ 76,478
Land Initial Cost	104,486
Building and Improvements Initial Cost	327,904
Adjustments and Costs to Land and Building Subsequent to Acquisition	30,986
Gross carrying amount - Land	103,894
Gross carrying amount - Building and improvements	359,482
Gross carrying amount - Total	463,376
Accumulated Depreciation	$ 88,599
Self storage facilities | MI
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	8
Debt	$ 5,588
Land Initial Cost	10,900
Building and Improvements Initial Cost	63,388
Adjustments and Costs to Land and Building Subsequent to Acquisition	4,594
Gross carrying amount - Land	10,900
Gross carrying amount - Building and improvements	67,982
Gross carrying amount - Total	78,882
Accumulated Depreciation	$ 9,011
Self storage facilities | MN
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	7
Debt	$ 0
Land Initial Cost	9,696
Building and Improvements Initial Cost	74,960
Adjustments and Costs to Land and Building Subsequent to Acquisition	6,095
Gross carrying amount - Land	9,696
Gross carrying amount - Building and improvements	81,055
Gross carrying amount - Total	90,751
Accumulated Depreciation	$ 5,613
Self storage facilities | MO
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	4
Debt	$ 0
Land Initial Cost	3,517
Building and Improvements Initial Cost	13,674
Adjustments and Costs to Land and Building Subsequent to Acquisition	3,374
Gross carrying amount - Land	3,474
Gross carrying amount - Building and improvements	17,091
Gross carrying amount - Total	20,565
Accumulated Depreciation	$ 7,292
Self storage facilities | MS
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	3
Debt	$ 0
Land Initial Cost	2,914
Building and Improvements Initial Cost	29,630
Adjustments and Costs to Land and Building Subsequent to Acquisition	1,298
Gross carrying amount - Land	2,914
Gross carrying amount - Building and improvements	30,928
Gross carrying amount - Total	33,842
Accumulated Depreciation	$ 3,244
Self storage facilities | NC
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	23
Debt	$ 6,684
Land Initial Cost	38,463
Building and Improvements Initial Cost	150,475
Adjustments and Costs to Land and Building Subsequent to Acquisition	10,399
Gross carrying amount - Land	38,461
Gross carrying amount - Building and improvements	160,876
Gross carrying amount - Total	199,337
Accumulated Depreciation	$ 18,159
Self storage facilities | NH
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	2
Debt	$ 0
Land Initial Cost	754
Building and Improvements Initial Cost	4,054
Adjustments and Costs to Land and Building Subsequent to Acquisition	1,353
Gross carrying amount - Land	817
Gross carrying amount - Building and improvements	5,344
Gross carrying amount - Total	6,161
Accumulated Depreciation	$ 2,716
Self storage facilities | NJ
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	62
Debt	$ 106,726
Land Initial Cost	138,417
Building and Improvements Initial Cost	605,834
Adjustments and Costs to Land and Building Subsequent to Acquisition	51,542
Gross carrying amount - Land	141,643
Gross carrying amount - Building and improvements	654,150
Gross carrying amount - Total	795,793
Accumulated Depreciation	$ 164,838
Self storage facilities | NM
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	10
Debt	$ 17,085
Land Initial Cost	30,806
Building and Improvements Initial Cost	63,495
Adjustments and Costs to Land and Building Subsequent to Acquisition	5,105
Gross carrying amount - Land	30,806
Gross carrying amount - Building and improvements	68,600
Gross carrying amount - Total	99,406
Accumulated Depreciation	$ 12,628
Self storage facilities | NV
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	14
Debt	$ 29,942
Land Initial Cost	15,252
Building and Improvements Initial Cost	74,376
Adjustments and Costs to Land and Building Subsequent to Acquisition	6,379
Gross carrying amount - Land	15,252
Gross carrying amount - Building and improvements	80,755
Gross carrying amount - Total	96,007
Accumulated Depreciation	$ 14,958
Self storage facilities | NY
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	28
Debt	$ 13,886
Land Initial Cost	121,945
Building and Improvements Initial Cost	237,795
Adjustments and Costs to Land and Building Subsequent to Acquisition	41,749
Gross carrying amount - Land	122,680
Gross carrying amount - Building and improvements	278,809
Gross carrying amount - Total	401,489
Accumulated Depreciation	$ 76,295
Self storage facilities | OH
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	16
Debt	$ 11,651
Land Initial Cost	17,568
Building and Improvements Initial Cost	49,287
Adjustments and Costs to Land and Building Subsequent to Acquisition	9,036
Gross carrying amount - Land	17,567
Gross carrying amount - Building and improvements	58,324
Gross carrying amount - Total	75,891
Accumulated Depreciation	$ 16,292
Self storage facilities | OR
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	8
Debt	$ 16,804
Land Initial Cost	15,066
Building and Improvements Initial Cost	68,044
Adjustments and Costs to Land and Building Subsequent to Acquisition	2,268
Gross carrying amount - Land	15,066
Gross carrying amount - Building and improvements	70,312
Gross carrying amount - Total	85,378
Accumulated Depreciation	$ 10,284
Self storage facilities | PA
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	21
Debt	$ 8,673
Land Initial Cost	35,104
Building and Improvements Initial Cost	190,966
Adjustments and Costs to Land and Building Subsequent to Acquisition	14,639
Gross carrying amount - Land	34,396
Gross carrying amount - Building and improvements	206,313
Gross carrying amount - Total	240,709
Accumulated Depreciation	$ 34,860
Self storage facilities | RI
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	2
Debt	$ 3,952
Land Initial Cost	3,191
Building and Improvements Initial Cost	6,926
Adjustments and Costs to Land and Building Subsequent to Acquisition	1,369
Gross carrying amount - Land	3,191
Gross carrying amount - Building and improvements	8,295
Gross carrying amount - Total	11,486
Accumulated Depreciation	$ 3,473
Self storage facilities | SC
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	23
Debt	$ 25,008
Land Initial Cost	36,617
Building and Improvements Initial Cost	148,900
Adjustments and Costs to Land and Building Subsequent to Acquisition	10,789
Gross carrying amount - Land	36,618
Gross carrying amount - Building and improvements	159,688
Gross carrying amount - Total	196,306
Accumulated Depreciation	$ 29,256
Self storage facilities | TN
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	21
Debt	$ 42,375
Land Initial Cost	34,740
Building and Improvements Initial Cost	138,399
Adjustments and Costs to Land and Building Subsequent to Acquisition	11,557
Gross carrying amount - Land	34,740
Gross carrying amount - Building and improvements	149,956
Gross carrying amount - Total	184,696
Accumulated Depreciation	$ 25,607
Self storage facilities | TX
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	101
Debt	$ 116,803
Land Initial Cost	173,040
Building and Improvements Initial Cost	635,935
Adjustments and Costs to Land and Building Subsequent to Acquisition	67,710
Gross carrying amount - Land	172,892
Gross carrying amount - Building and improvements	703,793
Gross carrying amount - Total	876,685
Accumulated Depreciation	$ 143,451
Self storage facilities | UT
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	10
Debt	$ 14,316
Land Initial Cost	9,008
Building and Improvements Initial Cost	39,295
Adjustments and Costs to Land and Building Subsequent to Acquisition	3,072
Gross carrying amount - Land	9,008
Gross carrying amount - Building and improvements	42,367
Gross carrying amount - Total	51,375
Accumulated Depreciation	$ 12,587
Self storage facilities | VA
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	50
Debt	$ 52,508
Land Initial Cost	150,324
Building and Improvements Initial Cost	470,969
Adjustments and Costs to Land and Building Subsequent to Acquisition	27,164
Gross carrying amount - Land	150,325
Gross carrying amount - Building and improvements	498,132
Gross carrying amount - Total	648,457
Accumulated Depreciation	$ 93,787
Self storage facilities | DC
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	9
Debt	$ 5,167
Land Initial Cost	13,762
Building and Improvements Initial Cost	60,926
Adjustments and Costs to Land and Building Subsequent to Acquisition	11,618
Gross carrying amount - Land	13,764
Gross carrying amount - Building and improvements	72,542
Gross carrying amount - Total	86,306
Accumulated Depreciation	$ 14,437
Self storage facilities | DC
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Store Count | store	1
Debt	$ 8,175
Land Initial Cost	14,394
Building and Improvements Initial Cost	18,172
Adjustments and Costs to Land and Building Subsequent to Acquisition	507
Gross carrying amount - Land	14,394
Gross carrying amount - Building and improvements	18,679
Gross carrying amount - Total	33,073
Accumulated Depreciation	2,865
Other corporate assets
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Debt	0
Land Initial Cost	0
Building and Improvements Initial Cost	1,323
Adjustments and Costs to Land and Building Subsequent to Acquisition	181,117
Gross carrying amount - Land	0
Gross carrying amount - Building and improvements	182,440
Gross carrying amount - Total	182,440
Accumulated Depreciation	57,041
Intangible tenant relationships and lease rights
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Debt	0
Land Initial Cost	0
Building and Improvements Initial Cost	147,020
Adjustments and Costs to Land and Building Subsequent to Acquisition	0
Gross carrying amount - Land	0
Gross carrying amount - Building and improvements	147,020
Gross carrying amount - Total	147,020
Accumulated Depreciation	130,561
Construction in Progress/Undeveloped Land
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Debt	0
Land Initial Cost	7,111
Building and Improvements Initial Cost	2,778
Adjustments and Costs to Land and Building Subsequent to Acquisition	56,441
Gross carrying amount - Land	3,576
Gross carrying amount - Building and improvements	62,754
Gross carrying amount - Total	66,330
Accumulated Depreciation	621
Right of use asset - finance lease
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items]
Debt	0
Land Initial Cost	0
Building and Improvements Initial Cost	0
Adjustments and Costs to Land and Building Subsequent to Acquisition	117,718
Gross carrying amount - Land	0
Gross carrying amount - Building and improvements	117,718
Gross carrying amount - Total	117,718
Accumulated Depreciation	$ 3,049