Real Estate Assets - Additional Information (Details) - Millbrook, NY - ft²	3 Months Ended	9 Months Ended
	Jun. 30, 2019	Sep. 30, 2019
Real Estate Properties [Line Items]
Gross square feet of traditional drive-up storage units and all-climate-controlled units	16,500
Estimate for expansion relating to construction cost		As of September 30, 2019, development costs for this project has been capitalized and are reflected in real estate assets, net on the Company’s consolidated balance sheet. We currently anticipate that the construction project will proceed accordingly, with construction completion approximately nine to twelve months from project commencement. However, there is no guarantee that we will complete this project in this timeframe or at all.