Investments in Unconsolidated Real Estate Entities - Schedule of Equity in Earnings of Unconsolidated Real Estate Ventures (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	$ 22,361	$ 11,274	$ 14,452
SmartStop Self Storage REIT, Inc. Preferred Stock
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	9,968	1,636	0
PRISA Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	2,229	2,327	2,338
Storage Portfolio II JV LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	559	291	79
Storage Portfolio I LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	1,636	1,809	1,886
VRS Self Storage, LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	3,509	3,583	3,640
ESS-NYFL JV LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	(331)	(96)	0
WICNN JV LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	1,878	1,373	622
Extra Space Northern Properties Six LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	1,088	1,091	1,014
Alan Jathoo JV LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	57	(47)	(12)
ESS Bristol Investments LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	(67)	(262)	(152)
GFN JV, LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	788	450	22
PR EXR Self Storage, LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	(211)	(443)	(75)
WCOT Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	0	0	359
Extra Space West Two LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	0	0	1,042
Extra Space West One LLC
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	0	0	2,526
Other minority owned stores
Schedule of Equity Method Investments [Line Items]
Equity in earnings and dividend income from unconsolidated real estate entities	$ 1,258	$ (438)	$ 1,163