Name:	gms_LongTermDebtMandatoryRedemptionAnnualExcessCashFlowForMandatoryPrincipalPrepaymentAmount
Namespace Prefix:	gms_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Represents the percentage of the annual excess cash flow required to be used for mandatory prepayment of the debt instrument.

No definition available.

Name:	gms_LongTermDebtMandatoryRedemptionPercentageOfAnnualExcessCashFlowForMandatoryPrincipalPrepayment
Namespace Prefix:	gms_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of the net proceeds of certain asset sales and issuances or incurrences of nonpermitted indebtedness required to be used for mandatory prepayment of the debt instrument.

No definition available.

Name:	gms_LongTermDebtMandatoryRedemptionPercentageOfNetProceedsOfCertainAssetSalesAndIssuancesOrIncurrencesOfNonpermittedIndebtednessForMandatoryPrincipalPrepayment
Namespace Prefix:	gms_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Write-off of amounts previously capitalized as debt issuance cost and unamortized debt discount (net of debt premium) that was originally recognized at the issuance of the instrument in an extinguishment of debt.

No definition available.

Name:	gms_WriteOffOfDeferredDebtIssuanceCostAndUnamortizedDiscountPremiumNet
Namespace Prefix:	gms_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

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.

No definition available.

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Name:	us-gaap_DebtInstrumentAxis=gms_SeniorSecuredTermLoanFacilities01April2014Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_DebtInstrumentAxis=gms_SecondLienTermLoanDue2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_StatementScenarioAxis=gms_AttainmentOfCertainTotalLeverageRatioTargetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: