Earnings per share of QTS Realty Trust, Inc.(Narrative) (Details) - shares shares in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Class A Common Stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive shares excluded from the computation of diluted net earning per share	6.7	6.6
Class O Units
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive shares excluded from the computation of diluted net earning per share	0.5
Series B Convertible preferred stock
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Antidilutive shares excluded from the computation of diluted net earning per share	6.7