Earnings per share of QTS Realty Trust, Inc. (Computation of Basic and Diluted Net Income per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Earnings per Share [Abstract]
Net income (loss)	$ (252)	$ 5,568
Loss (Income) attributable to noncontrolling interests	29	(691)
Preferred stock dividends	(328)
Earnings attributable to participating securities	(258)	(233)
Net income (loss) available to common stockholders after allocation of participating securities	$ (809)	$ 4,644
Weighted average shares outstanding-basic	50,279	47,485
Effect of Class O units and options to purchase Class A common stock and restricted Class A common stock on an "as if" converted basis		876
Weighted average shares outstanding-diluted	50,279	48,361
Basic net income (loss) per share	$ (0.02)	$ 0.10
Diluted net income (loss) per share	$ (0.02)	$ 0.10