Investment in Joint Ventures - Company's Share of Unconsolidated Joint Ventures' Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	$ 1,110	$ 1,048	$ 1,921	$ 2,020
Sovran HHF Storage Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	880	739	1,709	1,428
Sovran HHF Storage Holdings II LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	477	432	890	800
191 III Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	(1)	18	(16)	36
Life Storage-SERS Storage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	(74)	25	(120)	86
Life Storage-HIERS Storage LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	11		32
Review Avenue Partners LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments		(217)	(280)	(432)
SNL Orix Merrick, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	2	(16)	(3)	(32)
SNL/Orix 1200 McDonald Ave., LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	(11)		(23)
Urban Box Coralway Storage, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	(130)		(254)
N 32nd Street Self Storage, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	(13)		(35)
Iskalo Office Holdings, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	58	$ 67	110	$ 134
Bluebird Sanford Storage LP [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	(8)		(8)
Bluebird Ingram Storage LP [Member]
Schedule of Equity Method Investments [Line Items]
Income (loss) from equity method investments	$ (81)		$ (81)