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

No definition available.

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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

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Balance Type:	credit
Period Type:	instant

- 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=77997519&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=77997519&loc=d3e13476-108611

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-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

+ Details

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

- Definition

Debt instrument variable interest rate floor.

+ References

No definition available.

+ Details

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

- Definition

Increase annual interest expense due to hypothetical increase in applicable interest rate.

+ References

No definition available.

+ Details

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Namespace Prefix:	zgh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Details

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FAIR VALUE MEASUREMENTS (Narrative) (Details) - USD ($) $ in Millions			12 Months Ended
	Dec. 22, 2017	Jul. 22, 2016	Jun. 30, 2018	Jun. 30, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying value of the notes			$ 5,695.1	$ 5,537.7
Hypothetical annual interest expense			17.6
Term Loan Facility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying value of the notes			$ 1,751.3	1,912.7
Term Loan Facility \| LIBOR
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Spread on interest rate		2.75%
Term Loan Facility \| LIBOR \| Minimum
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Spread on interest rate	1.00%	1.00%	1.00%
Tranche One [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Debt instrument, face amount			$ 500.0
Tranche One [Member] \| LIBOR
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Spread on interest rate			2.00%
Floor rate			0.00%
Tranche Two [Member] \| LIBOR
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Spread on interest rate			2.25%
Floor rate			1.00%
Notes [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying value of the notes			$ 4,003.4	3,692.8
Fair value of the notes			3,986.5	3,895.7
Notes [Member] \| Term Loan Facility
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of the notes			1,772.3	1,930.5
Revolver [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Carrying value of the notes			$ 0.0	$ 0.0