Commitments and Contingencies - Additional Information (Details) $ in Thousands, ft² in Millions	Mar. 31, 2018 USD ($) ft² Property
Other Commitments [Line Items]
Number of industrial properties | Property	485
Gross leasable area (GLA) of industrial properties | ft²	60.1
Development Activity
Other Commitments [Line Items]
Number of industrial properties | Property	11
Gross leasable area (GLA) of industrial properties | ft²	4.2
Estimated total investment | $	$ 291,000
Estimated total investment remaining to be funded | $	$ 128,500