Investment in Real Estate - Additional Information (Details) $ in Thousands, ft² in Millions		12 Months Ended
		Dec. 31, 2018 USD ($) ft² Property	Dec. 31, 2017 USD ($) ft² Property	Dec. 31, 2016 USD ($) ft² Property
Real Estate Properties [Line Items]
Number of industrial properties | Property		458
Gross leasable area (GLA) of industrial properties | ft²		63.1
Proceeds from sale of industrial properties | $	[1]	$ 192,047	$ 236,059	$ 169,911
Gain on sale of real estate | $	[1]	81,600	131,269	68,202
Impairment of Real Estate | $		$ 2,756	$ 0	$ 0
Acquisition Activity
Real Estate Properties [Line Items]
Number of industrial properties | Property		10	8	6
Gross leasable area (GLA) of industrial properties | ft²		1.0	1.1	0.7
Purchase price of industrial properties acquired | $		$ 167,546	$ 174,209	$ 111,130
Disposition Activity
Real Estate Properties [Line Items]
Number of industrial properties | Property		53	60	63
Gross leasable area (GLA) of industrial properties | ft²		2.6	4.6	3.9
Impairment Activity
Real Estate Properties [Line Items]
Impairment of Real Estate | $		$ 2,756
Disposition with Impairment Activity
Real Estate Properties [Line Items]
Number of industrial properties | Property		1
Number of Land Parcels | Property		1

[1] (B) Gross proceeds and gain on sale of real estate include the sale of several land parcels for the years ended December 31, 2018, 2017 and 2016.