Noncontrolling Interest (Narrative) (Details) shares in Millions	12 Months Ended
	Dec. 31, 2017 shares	Dec. 31, 2016
Quality Tech LP ownership percentage in operating partnership	21.20%
Stock conversion ratio	1
Units redeemed for common stock	0.6
Qualitytech, LP
Quality Tech LP ownership percentage in operating partnership	11.40%	12.40%