Business Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Segment Reporting Information [Line Items]
Revenue	$ 312.0	$ 368.2	$ 637.7	$ 731.0
Operating income	46.8	65.2	66.0	146.2
Expenditures for long-lived assets	45.0	82.8	95.9	167.4
Depreciation and amortization	37.2	53.7	87.8	104.8
Assets	2,145.4		2,145.4		2,872.4
Segment Reporting Information, Additional Information [Abstract]
Total ownership interests in CyrusOne, Percentage	69.00%		69.00%
Loss from CyrusOne	(4.7)	0	(6.6)	0
Investment in CyrusOne	489.3		489.3		0
Wireline [Member]
Segment Reporting Information [Line Items]
Revenue	181.6	183.7	361.3	366.1
Operating income	48.9	54.7	99.0	111.9
Expenditures for long-lived assets	39.3	26.4	73.1	49.7
Depreciation and amortization	27.3	26.4	54.1	52.3
Assets	753.1		753.1		723.7
Wireless [Member]
Segment Reporting Information [Line Items]
Revenue	51.7	61.8	105.0	125.5
Operating income	11.4	15.8	12.1	30.9
Expenditures for long-lived assets	2.0	1.9	10.2	8.2
Depreciation and amortization	7.3	8.0	23.3	15.9
Assets	257.9		257.9		275.6
IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenue	86.0	77.3	170.5	150.5
Operating income	0.3	0.8	2.2	3.4
Expenditures for long-lived assets	3.7	2.5	4.9	4.7
Depreciation and amortization	2.5	2.3	5.0	3.9
Assets	45.2		45.2		43.3
Data Center Colocation [Member]
Segment Reporting Information [Line Items]
Revenue	0	54.0	15.6	106.6
Operating income	0	(1.9)	3.2	11.3
Expenditures for long-lived assets	0	52.0	7.7	104.8
Depreciation and amortization	0	17.0	5.2	32.6
Assets	0		0		1,208.5
Corporate [Member]
Segment Reporting Information [Line Items]
Operating income	(13.8)	(4.2)	(50.5)	(11.3)
Depreciation and amortization	0.1	0	0.2	0.1
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	(7.3)	(8.6)	(14.7)	(17.7)
Intersegment Eliminations [Member] | Wireline [Member]
Segment Reporting Information [Line Items]
Revenue	4.2	4.7	8.6	9.7
Intersegment Eliminations [Member] | Wireless [Member]
Segment Reporting Information [Line Items]
Revenue	0.6	0.6	1.2	1.2
Intersegment Eliminations [Member] | IT Services and Hardware [Member]
Segment Reporting Information [Line Items]
Revenue	2.5	1.7	4.5	3.6
Intersegment Eliminations [Member] | Data Center Colocation [Member]
Segment Reporting Information [Line Items]
Revenue	0	1.6	0.4	3.2
Intersegment Eliminations [Member] | Corporate [Member]
Segment Reporting Information [Line Items]
Assets	1,089.2		1,089.2		621.3
Sales [Member] | Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Revenue	$ 7.3	$ 8.6	$ 14.7	$ 17.7