Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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- Definition

Amount of long-term debt before deduction of unamortized discount or premium. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, with initial maturities beyond one year or the normal operating cycle, if longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 16

-Article 9

+ Details

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Balance Type:	credit
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- Definition

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13476-108611

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Minimum contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22(a)(2))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Details

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- Definition

Amount of unrealized gain (loss) related to the fair value of interest rate derivatives designated as fair value hedging instruments, as offset by the gain (loss) on the hedged item to the extent that the fair value hedge is determined to be effective.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4A

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4C

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35706170&loc=SL5624171-113959

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Hypothetical annual interest expense.

+ References

No definition available.

+ Details

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Namespace Prefix:	zayo_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Hypothetical increase to interest rate swap fair value.

+ References

No definition available.

+ Details

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Namespace Prefix:	zayo_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Hypothetical interest rate increase.

+ References

No definition available.

+ Details

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Namespace Prefix:	zayo_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Increase Decrease In Share Based Compensation

+ References

No definition available.

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

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- Details

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- Details

Name:	us-gaap_DebtInstrumentAxis=zayo_NewNotesMember
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- Details

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Fair Value Measurements (Narrative) (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended	3 Months Ended		6 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Sep. 30, 2014	Nov. 26, 2013
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Carrying value of the notes	$ 3,001,100us-gaap_DebtInstrumentCarryingAmount	$ 3,001,100us-gaap_DebtInstrumentCarryingAmount			$ 3,260,776us-gaap_DebtInstrumentCarryingAmount	$ 2,853,800us-gaap_DebtInstrumentCarryingAmount		$ 1,749,750us-gaap_DebtInstrumentCarryingAmount
Hypothetical annual interest expense	20,000zayo_HypotheticalAnnualInterestExpense
Hypothetical increase to interest rate swap fair value					15,234		14,000
Interest Rate Swap [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Hypothetical interest rate increase		1.00%			1.00%
Change in fair value of interest rate swap	(500)	1,500	(400)	1,900	4,656	(2,642)
CII [Member] \| Increase of 1x enterprise valuation multiple [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Stock-based compensation liability					57,070
Term Loan Facility [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Carrying value of the notes	1,981,800	1,981,800			1,990,123	1,580,705
Floor rate	1.00%				1.00%
Percentage over variable rate	3.00%				3.00%
Hypothetical interest rate increase	1.00%				1.00%
Hypothetical annual interest expense					20,108
Notes [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Carrying value of the notes	1,000,600	1,000,600			1,250,000	1,250,000
Fair value of the notes	$ 1,083,100	$ 1,083,100			$ 1,294,750	$ 1,364,375