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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
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Data Type:	num:percentItemType
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Period Type:	duration

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

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Name:	us-gaap_AllocatedShareBasedCompensationExpense
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Balance Type:	debit
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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.

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Data Type:	xbrli:stringItemType
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Number of shares authorized for issuance under share-based payment arrangement.

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Data Type:	xbrli:sharesItemType
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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Data Type:	xbrli:sharesItemType
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Price of a single share of a number of saleable stocks of a company.

No definition available.

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Data Type:	num:perShareItemType
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Period Type:	instant

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

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