Business Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenue	$ 292.9us-gaap_SalesRevenueNet	$ 282.2us-gaap_SalesRevenueNet
Operating income (loss)	37.1us-gaap_OperatingIncomeLoss	50.4us-gaap_OperatingIncomeLoss
Expenditures for long-lived assets	57.9	34.3
Depreciation and amortization	61.2	46.9
Assets	1,733.0us-gaap_Assets		1,820.7us-gaap_Assets
Segment Reporting Information, Additional Information [Abstract]
Loss (income) from CyrusOne equity method investment	3.1	(0.5)
Investment in CyrusOne	261.5us-gaap_EquityMethodInvestments		273.6us-gaap_EquityMethodInvestments
Continuing Operations [Member]
Segment Reporting Information [Line Items]
Expenditures for long-lived assets		28.7
Depreciation and amortization	32.6	31.1
Discontinued Operations [Member]
Segment Reporting Information [Line Items]
Revenue	4.4	44.7
Operating income (loss)	(37.4)	6.5
Expenditures for long-lived assets	0	(5.6)
Depreciation and amortization	28.6	15.8
Assets	16.4		49.3
Wireline [Member]
Segment Reporting Information [Line Items]
Revenue	188.1	183.6
Operating income (loss)	41.3	51.8
Expenditures for long-lived assets	54.0	26.2
Depreciation and amortization	29.5	28.1
Assets	861.4		833.2
IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenue	107.6	101.9
Operating income (loss)	1.1	5.4
Expenditures for long-lived assets	3.9	2.5
Depreciation and amortization	3.1	2.8
Assets	58.9		61.4
Corporate Segment [Member]
Segment Reporting Information [Line Items]
Operating income (loss)	(5.3)	(6.8)
Depreciation and amortization	0	0.2
Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenue	(2.8)	(3.3)
Intersegment Elimination [Member] \| Wireline [Member]
Segment Reporting Information [Line Items]
Revenue	0.3	0.2
Intersegment Elimination [Member] \| IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenue	2.5	3.1
Intersegment Elimination [Member] \| Corporate Segment [Member]
Segment Reporting Information [Line Items]
Assets	796.3		876.8
Sales [Member] \| Intersegment Elimination [Member]
Segment Reporting Information [Line Items]
Revenue	$ 2.8	$ 3.3

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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