Supplemental Guarantor Information - Condensed Consolidating Statements of Cash Flows (Details) - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	$ 66,000,000	$ 6,300,000
Capital expenditures	(62,400,000)	(57,900,000)
Dividends received from CyrusOne	2,100,000	6,000,000
Other investing activities	(100,000)	(100,000)
Net cash used in investing activities	(60,400,000)	(52,000,000)
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	28,900,000	7,500,000
Repayment of debt	(30,900,000)	(3,300,000)
Other financing activities	(500,000)	(400,000)
Net cash (used in) provided by financing activities	(5,100,000)	1,200,000
Increase (decrease) in cash and cash equivalents	500,000	(44,500,000)
Cash and cash equivalents at beginning of period	7,400,000	57,900,000
Cash and cash equivalents at end of period	7,900,000	13,400,000
Notes guaranteed by parent [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	66,000,000	6,300,000
Capital expenditures	(62,400,000)	(57,900,000)
Dividends received from CyrusOne	2,100,000	6,000,000
Distributions received from subsidiaries	0	0
Funding between Parent and subsidiaries, net	0	0
Other investing activities	(100,000)	(100,000)
Net cash used in investing activities	(60,400,000.0)	(52,000,000.0)
Funding between Parent and subsidiaries, net	0	0
Distributions paid to Parent	0	0
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	28,900,000	7,500,000
Repayment of debt	(30,900,000)	(3,300,000)
Other financing activities	(3,100,000)	(3,000,000)
Net cash (used in) provided by financing activities	(5,100,000)	1,200,000
Increase (decrease) in cash and cash equivalents	500,000	(44,500,000)
Cash and cash equivalents at beginning of period	7,400,000	57,900,000
Cash and cash equivalents at end of period	7,900,000	13,400,000
Notes guaranteed by parent [Member] | Parent Company [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	(21,700,000)	(23,500,000)
Capital expenditures	(100,000)	0
Dividends received from CyrusOne	0	0
Distributions received from subsidiaries	2,900,000	2,700,000
Funding between Parent and subsidiaries, net	0	0
Other investing activities	(100,000)	(100,000)
Net cash used in investing activities	2,700,000.0	2,600,000.0
Funding between Parent and subsidiaries, net	24,800,000	(20,400,000)
Distributions paid to Parent	0	0
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	0	0
Repayment of debt	(1,400,000)	(1,300,000)
Other financing activities	(3,100,000)	(3,000,000)
Net cash (used in) provided by financing activities	20,300,000	(24,700,000)
Increase (decrease) in cash and cash equivalents	1,300,000	(45,600,000)
Cash and cash equivalents at beginning of period	4,600,000	56,200,000
Cash and cash equivalents at end of period	5,900,000	10,600,000
Notes guaranteed by parent [Member] | Cincinnati Bell Telephone Company [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	63,600,000	35,700,000
Capital expenditures	(55,800,000)	(51,800,000)
Dividends received from CyrusOne	0	0
Distributions received from subsidiaries	0	0
Funding between Parent and subsidiaries, net	20,700,000	17,300,000
Other investing activities	0	0
Net cash used in investing activities	(35,100,000.0)	(34,500,000.0)
Funding between Parent and subsidiaries, net	0	0
Distributions paid to Parent	0	0
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	0	0
Repayment of debt	(28,400,000)	(1,000,000)
Other financing activities	0	0
Net cash (used in) provided by financing activities	(28,400,000)	(1,000,000)
Increase (decrease) in cash and cash equivalents	100,000	200,000
Cash and cash equivalents at beginning of period	1,000,000	1,000,000
Cash and cash equivalents at end of period	1,100,000	1,200,000
Notes guaranteed by parent [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	24,100,000	(5,900,000)
Capital expenditures	(6,500,000)	(6,100,000)
Dividends received from CyrusOne	2,100,000	6,000,000
Distributions received from subsidiaries	0	0
Funding between Parent and subsidiaries, net	2,900,000	10,900,000
Other investing activities	0	0
Net cash used in investing activities	(1,500,000.0)	10,800,000.0
Funding between Parent and subsidiaries, net	(48,400,000)	(7,800,000)
Distributions paid to Parent	(2,900,000)	(2,700,000)
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	28,900,000	7,500,000
Repayment of debt	(1,100,000)	(1,000,000)
Other financing activities	0	0
Net cash (used in) provided by financing activities	(23,500,000)	(4,000,000)
Increase (decrease) in cash and cash equivalents	(900,000)	900,000
Cash and cash equivalents at beginning of period	1,800,000	700,000
Cash and cash equivalents at end of period	900,000	1,600,000
Notes guaranteed by parent [Member] | Consolidation, Eliminations [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	0	0
Capital expenditures	0	0
Dividends received from CyrusOne	0	0
Distributions received from subsidiaries	(2,900,000)	(2,700,000)
Funding between Parent and subsidiaries, net	(23,600,000)	(28,200,000)
Other investing activities	0	0
Net cash used in investing activities	(26,500,000.0)	(30,900,000.0)
Funding between Parent and subsidiaries, net	23,600,000	28,200,000
Distributions paid to Parent	2,900,000	2,700,000
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	0	0
Repayment of debt	0	0
Other financing activities	0	0
Net cash (used in) provided by financing activities	26,500,000	30,900,000
Increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	0	0
Notes guaranteed by subsidiaries [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	66,000,000	6,300,000
Capital expenditures	(62,400,000)	(57,900,000)
Dividends received from CyrusOne	2,100,000	6,000,000
Distributions received from subsidiaries	0	0
Funding between Parent and subsidiaries, net	0	0
Other investing activities	(100,000)	(100,000)
Net cash used in investing activities	(60,400,000)	(52,000,000)
Funding between Parent and subsidiaries, net	0	0
Distributions paid to Parent	0	0
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	28,900,000	7,500,000
Repayment of debt	(30,900,000)	(3,300,000)
Other financing activities	(3,100,000)	(3,000,000)
Net cash (used in) provided by financing activities	(5,100,000)	1,200,000
Increase (decrease) in cash and cash equivalents	500,000	(44,500,000)
Cash and cash equivalents at beginning of period	7,400,000	57,900,000
Cash and cash equivalents at end of period	7,900,000	13,400,000
Notes guaranteed by subsidiaries [Member] | Parent Company [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	(21,700,000)	(23,500,000)
Capital expenditures	(100,000)	0
Dividends received from CyrusOne	0	0
Distributions received from subsidiaries	2,900,000	2,700,000
Funding between Parent and subsidiaries, net	0	0
Other investing activities	(100,000)	(100,000)
Net cash used in investing activities	2,700,000	2,600,000
Funding between Parent and subsidiaries, net	24,800,000	(20,400,000)
Distributions paid to Parent	0	0
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	0	0
Repayment of debt	(1,400,000)	(1,300,000)
Other financing activities	(3,100,000)	(3,000,000)
Net cash (used in) provided by financing activities	20,300,000	(24,700,000)
Increase (decrease) in cash and cash equivalents	1,300,000	(45,600,000)
Cash and cash equivalents at beginning of period	4,600,000	56,200,000
Cash and cash equivalents at end of period	5,900,000	10,600,000
Notes guaranteed by subsidiaries [Member] | Guarantor Subsidiaries [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	(8,200,000)	(19,200,000)
Capital expenditures	(6,500,000)	(6,100,000)
Dividends received from CyrusOne	2,100,000	6,000,000
Distributions received from subsidiaries	0	0
Funding between Parent and subsidiaries, net	13,500,000	20,400,000
Other investing activities	0	0
Net cash used in investing activities	9,100,000	20,300,000
Funding between Parent and subsidiaries, net	0	0
Distributions paid to Parent	0	0
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	0	0
Repayment of debt	(1,100,000)	(1,000,000)
Other financing activities	0	0
Net cash (used in) provided by financing activities	(1,100,000)	(1,000,000)
Increase (decrease) in cash and cash equivalents	(200,000)	100,000
Cash and cash equivalents at beginning of period	400,000	200,000
Cash and cash equivalents at end of period	200,000	300,000
Notes guaranteed by subsidiaries [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	95,900,000	49,000,000
Capital expenditures	(55,800,000)	(51,800,000)
Dividends received from CyrusOne	0	0
Distributions received from subsidiaries	0	0
Funding between Parent and subsidiaries, net	0	7,200,000
Other investing activities	0	0
Net cash used in investing activities	(55,800,000)	(44,600,000)
Funding between Parent and subsidiaries, net	(38,300,000)	(7,200,000)
Distributions paid to Parent	(2,900,000)	(2,700,000)
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	28,900,000	7,500,000
Repayment of debt	(28,400,000)	(1,000,000)
Other financing activities	0	0
Net cash (used in) provided by financing activities	(40,700,000)	(3,400,000)
Increase (decrease) in cash and cash equivalents	(600,000)	1,000,000
Cash and cash equivalents at beginning of period	2,400,000	1,500,000
Cash and cash equivalents at end of period	1,800,000	2,500,000
Notes guaranteed by subsidiaries [Member] | Consolidation, Eliminations [Member]
Condensed Consolidating Statements of Cash Flows
Cash flows provided by (used in) operating activities	0	0
Capital expenditures	0	0
Dividends received from CyrusOne	0	0
Distributions received from subsidiaries	(2,900,000)	(2,700,000)
Funding between Parent and subsidiaries, net	(13,500,000)	(27,600,000)
Other investing activities	0	0
Net cash used in investing activities	(16,400,000)	(30,300,000)
Funding between Parent and subsidiaries, net	13,500,000	27,600,000
Distributions paid to Parent	2,900,000	2,700,000
Net increase (decrease) in corporate credit and receivables facilities with initial maturities less than 90 days	0	0
Repayment of debt	0	0
Other financing activities	0	0
Net cash (used in) provided by financing activities	16,400,000	30,300,000
Increase (decrease) in cash and cash equivalents	0	0
Cash and cash equivalents at beginning of period	0	0
Cash and cash equivalents at end of period	$ 0	$ 0