Supplemental Cash Flow Information (Tables)

12 Months Ended

Dec. 31, 2017

Supplemental Cash Flow Information [Abstract]

Schedule of Cash Flow, Supplemental Disclosures [Table Text Block]

	Year Ended December 31,
(dollars in millions)	2017			2016		2015
Capitalized interest expense	$	0.7		$	0.7	$	1.1
Cash paid/(received) for:
Interest	65.7			71.1		108.5
Income taxes, net of refunds	(12.9		)	1.7		8.8
Noncash investing and financing activities:
Accrual of CyrusOne dividends	—			1.1		2.1
Acquisition of property by assuming debt and other financing arrangements	17.3			12.0		5.8
Acquisition of property on account	12.0			23.8		34.6