Investment in Real Estate Inestment in Real Estate - Summary of Industrial Property Dispositions (Details) $ in Thousands, ft² in Millions		12 Months Ended
		Dec. 31, 2016 USD ($) ft² Property	Dec. 31, 2015 USD ($) ft² Property	Dec. 31, 2014 USD ($) ft² Property
Real Estate [Abstract]
Number of industrial properties sold | Property		63	66	29
Gross leasable area (GLA) of industrial properties sold | ft²		3.9	3.8	2.0
Proceeds from sale of industrial properties	[1]	$ 169,911	$ 158,429	$ 102,596
Gain on sale of real estate	[1]	$ 68,202	$ 48,906	$ 25,905

[1] (A) Gross proceeds from the sale of real estate and gain on sale of real estate includes the sale of several land parcels for years ended December 31, 2015 and 2014.