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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of common stock price based on closing price at the beginning or end of the last day of the purchase period.

No definition available.

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

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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

Price of a single share of a number of saleable stocks of a company.

No definition available.

Name:	us-gaap_SharePrice
Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	instant

Number of shares issued during the period as a result of an employee stock purchase plan.

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