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Long-Term Debt (Narrative) (Details) - USD ($)					3 Months Ended			6 Months Ended		12 Months Ended
Long-Term Debt (Narrative) (Details) - USD ($)	May. 06, 2015	Dec. 31, 2014	Dec. 15, 2014	Jul. 02, 2012	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Jun. 30, 2015	Mar. 09, 2015	Jan. 23, 2015	Aug. 13, 2012
Debt Instrument [Line Items]
Loss on extinguishment of debt							$ (30,900,000)		$ (30,900,000)
Payment of early redemption fees on debt extinguished									23,800,000
Debt issuance cost								$ 99,500,000
Redemption of notes								8,300,000	259,700,000
Debt obligations					$ 3,744,100,000			3,744,100,000		$ 3,752,400,000
Outstanding letters of credit					9,200,000			9,200,000
Unamortized debt issuance cost					66,200,000			66,200,000		71,000,000
Accumulated amortization					33,300,000			33,300,000		28,300,000
Unamortized debt issuance related interest					2,500,000		3,800,000	5,000,000	7,500,000
8.125% Senior Secured Notes due 2020
Debt Instrument [Line Items]
Redemption of notes			$ 75,000,000
10.125% Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount				$ 500,000,000
Interest rate				10.125%
Maturity date				2020
Redemption premium							23,800,000
6.00% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Cumulative proceeds from issuance of private placement								1,437,300,000
January Notes Offering [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 700,000,000
March Notes Offering [Member]
Debt Instrument [Line Items]
Debt instrument, face amount											$ 730,000,000
Premium on debt being accreted					$ 7,300,000			$ 7,300,000
Debt Instrument Issuance At Premium Price Percentage					1.00%
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Notional amount of derivative													$ 750,000,000
Derivative, maturity date								Jun. 30, 2017
Derivative, fixed interest rate													1.67%
Derivative, floor rate													1.25%
Change in fair value of interest rate swap					$ 1,000,000		1,500,000	$ 600,000	(500,000)
Interest Rate Derivative Liabilities, at Fair Value					$ 3,500,000			3,500,000		4,100,000
December 15, 2014 [Member] \| 8.125% Senior Secured Notes due 2020
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage		108.125%
Zayo Group, LLC [Member]
Debt Instrument [Line Items]
Loss on extinguishment of debt							$ (30,900,000)		(30,900,000)
Payment of early redemption fees on debt extinguished									23,800,000
Redemption of notes								$ 7,100,000	$ 254,400,000
Revolver [Member]
Debt Instrument [Line Items]
Percentage of excess revolver committed to debt payments								35.00%
Standby Letter Of Credit [Member]
Debt Instrument [Line Items]
Unused commitment, percentage								0.25%
Secured Debt [Member] \| 8.125% Senior Secured Notes due 2020
Debt Instrument [Line Items]
Interest rate						8.125%
Maturity date					2020
Loss on extinguishment of debt						$ 105.75
Redemption of notes						675,000,000
Redemption premium						$ 38,800,000
Secured Debt [Member] \| Revolver [Member]
Debt Instrument [Line Items]
Line of credit facility maturity date								Apr. 17, 2020
Outstanding letters of credit increased					$ 50,000,000			$ 50,000,000
Outstanding letters of credit					0			0
Available borrowing capacity					440,800,000			$ 440,800,000
Secured Debt [Member] \| Revolver [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Unused commitment, percentage								0.25%
Secured Debt [Member] \| Revolver [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Unused commitment, percentage								0.375%
Secured Debt [Member] \| Revolver [Member] \| LIBOR [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Revolver interest rate								2.00%
Secured Debt [Member] \| Revolver [Member] \| LIBOR [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Revolver interest rate								3.00%
Unsecured Debt [Member]
Debt Instrument [Line Items]
Premium on debt being accreted					$ 6,700,000			$ 6,700,000		$ 7,100,000
Unsecured Debt [Member] \| 10.125% Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Interest rate					10.125%			10.125%		10.125%
Maturity date								2020		2020
Redemption of notes			$ 174,400,000
Debt obligations					$ 325,600,000			$ 325,600,000		$ 325,600,000
Unsecured Debt [Member] \| 6.00% Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Interest rate					6.00%			6.00%		6.00%	6.00%
Maturity date					2023			2023		2023
Line of credit facility maturity date								Apr. 01, 2023
Debt obligations					$ 1,430,000,000			$ 1,430,000,000		$ 1,430,000,000
Unsecured Debt [Member] \| 6.375% Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount	$ 350,000,000
Interest rate	6.375%				6.375%			6.375%		6.375%
Maturity date	2025							2025		2025
Line of credit facility maturity date	May 15, 2025
Loss on extinguishment of debt	$ (8,400,000)
Debt obligations	344,500,000				$ 350,000,000			$ 350,000,000		$ 350,000,000
Unsecured Debt [Member] \| December 15, 2014 [Member] \| 10.125% Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Debt instrument, redemption price, percentage			110.125%
2020 Unsecured Notes [Member]
Debt Instrument [Line Items]
Secured debt ratio					4.50			4.50
Total indebtedness ratio					5.25%			5.25%
2023 Unsecured Notes [Member]
Debt Instrument [Line Items]
Secured debt ratio					4.50			4.50
Total indebtedness ratio					6.00%			6.00%
2025 Unsecured Notes [Member]
Debt Instrument [Line Items]
Secured debt ratio					4.50			4.50
Total indebtedness ratio					6.00%			6.00%
Term Loan Facility due 2021 [Member]
Debt Instrument [Line Items]
Maturity date								2021		2021
Discount on debt					$ 18,300,000			$ 18,300,000		$ 19,800,000
Debt obligations					$ 1,638,500,000			$ 1,638,500,000		$ 1,646,800,000
Percentage of effective interest rate					3.75%			3.75%		3.75%
Term Loan Facility due 2021 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Revolver interest rate								2.75%
Term Loan Facility \| Amendment and Restatement Agreement [Member]
Debt Instrument [Line Items]
Line of credit facility maximum borrowing capacity	450,000,000
Payment towards principal	$ 4,100,000
Percentage of excess cash flows committed to debt payments.	50.00%
Term Loan Facility \| LIBOR [Member] \| Amendment and Restatement Agreement [Member]
Debt Instrument [Line Items]
Revolver interest rate	2.75%
Interest rate decrease (basis point)	(25.00%)
Term Loan Facility \| LIBOR [Member] \| Minimum [Member] \| Amendment and Restatement Agreement [Member]
Debt Instrument [Line Items]
Revolver interest rate	1.00%
Unamortized Debt Issuance Costs [Member]
Debt Instrument [Line Items]
Loss on extinguishment of debt										$ (23,200,000)
Unamortized Debt Discount
Debt Instrument [Line Items]
Loss on extinguishment of debt								$ 7,100,000