Store Acquisitions and Dispositions - Schedule of Operating Properties Acquired (Detail)	3 Months Ended				6 Months Ended
	Jun. 30, 2018 USD ($) store shares	Mar. 31, 2018 USD ($) store shares	Jun. 30, 2017 USD ($) store shares	Mar. 31, 2017 USD ($) store shares	Jun. 30, 2018 USD ($) store shares	Jun. 30, 2017 USD ($) store shares
Asset Acquisitions [Abstract]
Number of Stores | store	17	5	3	2	22	5
Total consideration transferred	$ 237,284,000	$ 70,787,000	$ 34,641,000	$ 25,556,000	$ 308,071,000	$ 60,197,000
Cash Paid	148,648,000	70,171,000	16,608,000	25,541,000	218,819,000	42,149,000
Loan Assumed	87,500,000	0	9,463,000	0	87,500,000	9,463,000
Non- controlling interests	0	0	1,827,000	0	0	1,827,000
Investments in Real Estate Ventures	(1,024,000)	489,000	0	0	(535,000)	0
Net Liabilities/ (Assets) Assumed	283,000	127,000	(67,000)	15,000	410,000	(52,000)
Value of OP Units Issued	$ 1,877,000	$ 0	$ 6,810,000	$ 0	$ 1,877,000	$ 6,810,000
Number of OP Units Issued | shares	21,768	0	272,400	0	21,768	272,400
Real estate assets, net	$ 237,284,000	$ 70,787,000	$ 34,641,000	$ 25,556,000	$ 308,071,000	$ 60,197,000
Number of stores acquired | store	15				15
Gain (loss) on sale of properties					$ 0