Supplemental Guarantor Information - Condensed Consolidating Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			$ 98.1	$ 32.7
Capital expenditures	$ (59.2)	$ (74.6)	(121.6)	(132.5)
Dividends received from CyrusOne			4.9	15.0
Proceeds from sale of CyrusOne			142.5	426.0
Other investing activities			(0.7)	(0.1)
Net cash provided by investing activities			25.1	308.4
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			15.4	(16.6)
Repayment of debt			(124.6)	(361.4)
Debt issuance costs			(1.9)	(0.4)
Common stock repurchase			(4.6)	0.0
Other financing activities			(0.1)	(0.6)
Cash flows provided by (used in) financing activities			(121.0)	(384.2)
Increase (decrease) in cash and cash equivalents			2.2	(43.1)
Cash and cash equivalents at beginning of period			7.4	57.9
Cash and cash equivalents at end of period	9.6	14.8	9.6	14.8
Notes guaranteed by parent [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			98.1	32.7
Capital expenditures			(121.6)	(132.5)
Dividends received from CyrusOne			4.9	15.0
Proceeds from sale of CyrusOne			142.5	426.0
Proceeds from sale of assets				0.1
Distributions received from subsidiaries			0.0	0.0
Funding between parent and subsidiaries, net			0.0	0.0
Other investing activities			(0.7)	(0.2)
Net cash provided by investing activities			25.1	308.4
Funding between parent and subsidiaries, net			0.0	0.0
Distributions paid to Parent			0.0	0.0
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			15.4	(16.6)
Repayment of debt			(124.6)	(361.4)
Debt issuance costs			(1.9)	(0.4)
Common stock repurchase			(4.6)
Other financing activities			(5.3)	(5.8)
Cash flows provided by (used in) financing activities			(121.0)	(384.2)
Increase (decrease) in cash and cash equivalents			2.2	(43.1)
Cash and cash equivalents at beginning of period			7.4	57.9
Cash and cash equivalents at end of period	9.6	14.8	9.6	14.8
Notes guaranteed by parent [Member] | Consolidation, Eliminations [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			0.0	0.0
Capital expenditures			0.0	0.0
Dividends received from CyrusOne			0.0	0.0
Proceeds from sale of CyrusOne			0.0	0.0
Proceeds from sale of assets				0.0
Distributions received from subsidiaries			(5.9)	(5.3)
Funding between parent and subsidiaries, net			121.1	341.2
Other investing activities			0.0	0.0
Net cash provided by investing activities			115.2	335.9
Funding between parent and subsidiaries, net			(121.1)	(341.2)
Distributions paid to Parent			5.9	5.3
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			0.0	0.0
Repayment of debt			0.0	0.0
Debt issuance costs			0.0	0.0
Common stock repurchase			0.0
Other financing activities			0.0	0.0
Cash flows provided by (used in) financing activities			(115.2)	(335.9)
Increase (decrease) in cash and cash equivalents			0.0	0.0
Cash and cash equivalents at beginning of period			0.0	0.0
Cash and cash equivalents at end of period	0.0	0.0	0.0	0.0
Notes guaranteed by parent [Member] | Parent Company [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			(39.0)	(22.9)
Capital expenditures			(0.2)	(0.1)
Dividends received from CyrusOne			0.0	0.0
Proceeds from sale of CyrusOne			0.0	0.0
Proceeds from sale of assets				0.0
Distributions received from subsidiaries			5.9	5.3
Funding between parent and subsidiaries, net			0.0	0.0
Other investing activities			(0.7)	(0.2)
Net cash provided by investing activities			5.0	5.0
Funding between parent and subsidiaries, net			136.4	333.6
Distributions paid to Parent			0.0	0.0
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			0.0	0.0
Repayment of debt			(87.5)	(357.2)
Debt issuance costs			(1.7)	(0.2)
Common stock repurchase			(4.6)
Other financing activities			(5.3)	(5.8)
Cash flows provided by (used in) financing activities			37.3	(29.6)
Increase (decrease) in cash and cash equivalents			3.3	(47.5)
Cash and cash equivalents at beginning of period			4.6	56.2
Cash and cash equivalents at end of period	7.9	8.7	7.9	8.7
Notes guaranteed by parent [Member] | Cincinnati Bell Telephone Company [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			131.2	103.9
Capital expenditures			(108.2)	(119.8)
Dividends received from CyrusOne			0.0	0.0
Proceeds from sale of CyrusOne			0.0	0.0
Proceeds from sale of assets				0.1
Distributions received from subsidiaries			0.0	0.0
Funding between parent and subsidiaries, net			11.9	20.3
Other investing activities			0.0	0.0
Net cash provided by investing activities			(96.3)	(99.4)
Funding between parent and subsidiaries, net			0.0	0.0
Distributions paid to Parent			0.0	0.0
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			0.0	0.0
Repayment of debt			(35.1)	(2.3)
Debt issuance costs			0.0	0.0
Common stock repurchase			0.0
Other financing activities			0.0	0.0
Cash flows provided by (used in) financing activities			(35.1)	(2.3)
Increase (decrease) in cash and cash equivalents			(0.2)	2.2
Cash and cash equivalents at beginning of period			1.0	1.0
Cash and cash equivalents at end of period	0.8	3.2	0.8	3.2
Notes guaranteed by parent [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			5.9	(48.3)
Capital expenditures			(13.2)	(12.6)
Dividends received from CyrusOne			4.9	15.0
Proceeds from sale of CyrusOne			142.5	426.0
Proceeds from sale of assets				0.0
Distributions received from subsidiaries			0.0	0.0
Funding between parent and subsidiaries, net			(133.0)	(361.5)
Other investing activities			0.0	0.0
Net cash provided by investing activities			1.2	66.9
Funding between parent and subsidiaries, net			(15.3)	7.6
Distributions paid to Parent			(5.9)	(5.3)
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			15.4	(16.6)
Repayment of debt			(2.0)	(1.9)
Debt issuance costs			(0.2)	(0.2)
Common stock repurchase			0.0
Other financing activities			0.0	0.0
Cash flows provided by (used in) financing activities			(8.0)	(16.4)
Increase (decrease) in cash and cash equivalents			(0.9)	2.2
Cash and cash equivalents at beginning of period			1.8	0.7
Cash and cash equivalents at end of period	0.9	2.9	0.9	2.9
Notes guaranteed by subsidiaries [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			98.1	32.7
Capital expenditures			(121.6)	(132.5)
Dividends received from CyrusOne			4.9	15.0
Proceeds from sale of CyrusOne			142.5	426.0
Proceeds from sale of assets				0.1
Distributions received from subsidiaries			0.0	0.0
Funding between parent and subsidiaries, net			0.0	0.0
Other investing activities			(0.7)	(0.2)
Net cash provided by investing activities			25.1	308.4
Funding between parent and subsidiaries, net			0.0	0.0
Distributions paid to Parent			0.0	0.0
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			15.4	(16.6)
Repayment of debt			(124.6)	(361.4)
Debt issuance costs			(1.9)	(0.4)
Common stock repurchase			(4.6)
Other financing activities			(5.3)	(5.8)
Cash flows provided by (used in) financing activities			(121.0)	(384.2)
Increase (decrease) in cash and cash equivalents			2.2	(43.1)
Cash and cash equivalents at beginning of period			7.4	57.9
Cash and cash equivalents at end of period	9.6	14.8	9.6	14.8
Notes guaranteed by subsidiaries [Member] | Consolidation, Eliminations [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			0.0	0.0
Capital expenditures			0.0	0.0
Dividends received from CyrusOne			0.0	0.0
Proceeds from sale of CyrusOne			0.0	0.0
Proceeds from sale of assets				0.0
Distributions received from subsidiaries			(5.9)	(5.3)
Funding between parent and subsidiaries, net			119.6	342.2
Other investing activities			0.0	0.0
Net cash provided by investing activities			113.7	336.9
Funding between parent and subsidiaries, net			(119.6)	(342.2)
Distributions paid to Parent			5.9	5.3
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			0.0	0.0
Repayment of debt			0.0	0.0
Debt issuance costs			0.0	0.0
Common stock repurchase			0.0
Other financing activities			0.0	0.0
Cash flows provided by (used in) financing activities			(113.7)	(336.9)
Increase (decrease) in cash and cash equivalents			0.0	0.0
Cash and cash equivalents at beginning of period			0.0	0.0
Cash and cash equivalents at end of period	0.0	0.0	0.0	0.0
Notes guaranteed by subsidiaries [Member] | Parent Company [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			(39.0)	(22.9)
Capital expenditures			(0.2)	(0.1)
Dividends received from CyrusOne			0.0	0.0
Proceeds from sale of CyrusOne			0.0	0.0
Proceeds from sale of assets				0.0
Distributions received from subsidiaries			5.9	5.3
Funding between parent and subsidiaries, net			0.0	0.0
Other investing activities			(0.7)	(0.2)
Net cash provided by investing activities			5.0	5.0
Funding between parent and subsidiaries, net			136.4	333.6
Distributions paid to Parent			0.0	0.0
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			0.0	0.0
Repayment of debt			(87.5)	(357.2)
Debt issuance costs			(1.7)	(0.2)
Common stock repurchase			(4.6)
Other financing activities			(5.3)	(5.8)
Cash flows provided by (used in) financing activities			37.3	(29.6)
Increase (decrease) in cash and cash equivalents			3.3	(47.5)
Cash and cash equivalents at beginning of period			4.6	56.2
Cash and cash equivalents at end of period	7.9	8.7	7.9	8.7
Notes guaranteed by subsidiaries [Member] | Guarantor Subsidiaries [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			(20.2)	(40.4)
Capital expenditures			(13.2)	(12.6)
Dividends received from CyrusOne			4.9	15.0
Proceeds from sale of CyrusOne			142.5	426.0
Proceeds from sale of assets				0.0
Distributions received from subsidiaries			0.0	0.0
Funding between parent and subsidiaries, net			(112.1)	(385.0)
Other investing activities			0.0	0.0
Net cash provided by investing activities			22.1	43.4
Funding between parent and subsidiaries, net			0.0	0.0
Distributions paid to Parent			0.0	0.0
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			0.0	0.0
Repayment of debt			(2.0)	(1.9)
Debt issuance costs			0.0	0.0
Common stock repurchase			0.0
Other financing activities			0.0	0.0
Cash flows provided by (used in) financing activities			(2.0)	(1.9)
Increase (decrease) in cash and cash equivalents			(0.1)	1.1
Cash and cash equivalents at beginning of period			0.4	0.2
Cash and cash equivalents at end of period	0.3	1.3	0.3	1.3
Notes guaranteed by subsidiaries [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities			157.3	96.0
Capital expenditures			(108.2)	(119.8)
Dividends received from CyrusOne			0.0	0.0
Proceeds from sale of CyrusOne			0.0	0.0
Proceeds from sale of assets				0.1
Distributions received from subsidiaries			0.0	0.0
Funding between parent and subsidiaries, net			(7.5)	42.8
Other investing activities			0.0	0.0
Net cash provided by investing activities			(115.7)	(76.9)
Funding between parent and subsidiaries, net			(16.8)	8.6
Distributions paid to Parent			(5.9)	(5.3)
Net (decrease) increase in corporate credit and receivables facilities with initial maturities less than 90 days			15.4	(16.6)
Repayment of debt			(35.1)	(2.3)
Debt issuance costs			(0.2)	(0.2)
Common stock repurchase			0.0
Other financing activities			0.0	0.0
Cash flows provided by (used in) financing activities			(42.6)	(15.8)
Increase (decrease) in cash and cash equivalents			(1.0)	3.3
Cash and cash equivalents at beginning of period			2.4	1.5
Cash and cash equivalents at end of period	$ 1.4	$ 4.8	$ 1.4	$ 4.8