Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 4.4	$ (5.3)	$ 19.1	$ (19.0)
Other comprehensive income (loss):
Foreign currency translation adjustments	(0.7)	(0.4)	(0.8)	(0.4)
Comprehensive income (loss)	3.7	(5.7)	18.3	(19.4)
Comprehensive loss attributable to noncontrolling interests	0.0	(0.7)	0.0	(4.6)
Comprehensive income (loss) attributable to CyrusOne Inc.	$ 3.7	$ (5.0)	$ 18.3	$ (14.8)