Investment in Real Estate - Additional Information (Detail) $ in Thousands, ft² in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2015 USD ($) ft² Property	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) ft² Property	Sep. 30, 2014 USD ($) Property	Dec. 31, 2014 Property
Real Estate [Abstract]
Number of industrial properties acquired			3
Gross leasable area (GLA) of industrial properties acquired | ft²			0.6
Purchase price of acquisitions | $	$ 72,961		$ 72,961
Number of industrial properties held for sale	7		7
Gross leasable area (GLA) of industrial properties held for sale | ft²	0.3		0.3
Number of industrial properties sold			15
Gross leasable area (GLA) of industrial properties sold | ft²			1.0
Proceeds from the sale of industrial properties | $			$ 50,060
Gain on sale of real estate | $			13,084	$ 14,483
Number of sold industrial properties included in discontinued operations				20	29
Impairment of Real Estate | $	$ 626	$ 0	$ 626	$ 0