Segment Reporting - Segment Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Segment Reporting Information, Additional Information
Assets	$ 2,267,587	$ 2,304,553
Operating Segments | Net Lease
Segment Reporting Information, Additional Information
Assets	1,402,568	1,461,385
Operating Segments | Self Storage
Segment Reporting Information, Additional Information
Assets	383,430	386,682
Operating Segments | Multi-Family
Segment Reporting Information, Additional Information
Assets	319,377	313,925
Corporate
Segment Reporting Information, Additional Information
Assets	97,736	78,099
All Other
Segment Reporting Information, Additional Information
Assets	$ 64,476	$ 64,462