Acquisitions of Real Estate - Additional Information (Detail) (QualityTech, LP [Member], USD $)	1 Months Ended	9 Months Ended		12 Months Ended
	Feb. 28, 2013	Sep. 30, 2013 sqft	Sep. 30, 2012	Dec. 31, 2012
QualityTech, LP [Member]
Loans At Acquisition Date [Line Items]
Cash consideration paid for acquisition	$ 10,250,000	$ 102,924,000	$ 86,351,000
Debt finance obtained for acquisition	10,250,000
Transaction costs incurred related to acquisition		600,000
Aggregate costs related to acquisition		21,200,000
Area Of former semiconductor plant		700,000
Aggregate consideration related to acquisition				$ 63,300,000