Noncontrolling Interest - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Jan. 25, 2013
Noncontrolling Interest [Line Items]
Partnership units, conversion basis into common stock (in shares)	1
Redemption value of noncontrolling interests	$ 887
Redemption value of noncontrolling interests based on closing price (usd per share)	$ 20.83	$ 19.00
CyrusOne Inc. and CyrusOne GP [Member]
Noncontrolling Interest [Line Items]
Number of outstanding partnership units purchased	21,900,000
Percentage of outstanding partnership units purchased	33.90%
Cincinnati Bell Inc. [Member]
Noncontrolling Interest [Line Items]
Percentage of retained ownership	66.10%
Number of operating partnership units owned	42,600,000
Ownership percentage	65.30%