Investments in Unconsolidated Real Estate Ventures - Schedule of Investments in Unconsolidated Real Estate Ventures (Details) $ in Thousands	1 Months Ended	3 Months Ended
	Jan. 31, 2019 USD ($) store	Mar. 31, 2019 USD ($) property store	Mar. 31, 2018 USD ($) store	Jan. 01, 2019	Dec. 31, 2018 USD ($)	Jan. 01, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Number of Stores | store		14	5
Cash Paid		$ 202,890	$ 70,171
Number of Stores | property		224
Investment balance		$ 116,459			$ 80,129
PRISA Self Storage LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		85
Equity Ownership %		4.00%
Excess Profit %		4.00%
Investment balance		$ 9,292			9,334
Storage Portfolio II JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		36
Equity Ownership %		10.00%
Excess Profit %		30.00%
Investment balance		$ (4,539)			(4,233)
Storage Portfolio I LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		24
Equity Ownership %		34.00%				34.00%	25.00%
Excess Profit %		49.00%				49.00%	40.00%
Investment balance		$ (38,186)			(38,129)
VRS Self Storage, LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		16
Equity Ownership %		45.00%
Excess Profit %		54.00%
Investment balance		$ 18,002			18,281
Extra Space Northern Properties Six LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		10
Equity Ownership %		10.00%
Excess Profit %		35.00%
Investment balance		$ (1,793)			(1,700)
WICNN JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		9
Equity Ownership %		10.00%
Excess Profit %		25.00%
Investment balance		$ 32,859			26,885
Alan Jathoo JV LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		9
Equity Ownership %		10.00%
Excess Profit %		10.00%
Investment balance		$ 8,132			8,180
ESS Bristol Investments LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		8
Equity Ownership %		10.00%
Excess Profit %		28.00%
Investment balance		$ 3,025			2,331
GFN JV, LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		5
Equity Ownership %		10.00%
Excess Profit %		25.00%
Investment balance		$ 12,429			10,586
Extra Space West Two LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		0
Equity Ownership %		5.00%
Excess Profit %		40.00%
Investment balance		$ 0			3,818
Extra Space West One LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		0
Equity Ownership %		5.00%
Excess Profit %		40.00%
Investment balance		$ 0			(1,038)
Other minority owned stores
Schedule of Equity Method Investments [Line Items]
Number of Stores | property		22
Investment balance		$ 77,238			$ 45,814
Other minority owned stores | Minimum
Schedule of Equity Method Investments [Line Items]
Equity Ownership %		10.00%
Excess Profit %		19.00%
Other minority owned stores | Maximum
Schedule of Equity Method Investments [Line Items]
Equity Ownership %		50.00%
Excess Profit %		50.00%
Extra Space West One and Two LLC
Schedule of Equity Method Investments [Line Items]
Number of Stores | store	12
Cash Paid	$ 172,505
Equity Ownership %				100.00%
Percentage interest purchased	95.00%