Segment Reporting - Segment Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Segment Reporting Information, Additional Information
Assets	$ 2,432,861	$ 2,330,997
Net Lease
Segment Reporting Information, Additional Information
Assets	1,600,618	1,572,437
Self Storage
Segment Reporting Information, Additional Information
Assets	397,470	398,944
Multi-family
Segment Reporting Information, Additional Information
Assets	292,707	256,875
Corporate
Segment Reporting Information, Additional Information
Assets	77,684	35,812
All Other
Segment Reporting Information, Additional Information
Assets	$ 64,382	$ 66,929