Number Of Acquisitions Completed

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- Definition

Number of Branch Locations

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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.

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No definition available.

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- Definition

Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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- Definition

The number of businesses acquired by the entity during the period.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Acquisitions - Narrative (Details) $ in Thousands	3 Months Ended								12 Months Ended
Acquisitions - Narrative (Details) $ in Thousands	Dec. 31, 2019 USD ($) branch	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) acquisition branch	Dec. 31, 2018 USD ($) acquisition	Oct. 01, 2019 branch	May 01, 2019 branch	Oct. 01, 2018 location	Aug. 01, 2018 location	Feb. 01, 2018 location
Business Acquisition [Line Items]
Number of branch locations \| branch	175								175
Net sales	$ 514,841	$ 564,906	$ 559,911	$ 514,872	$ 516,159	$ 542,273	$ 522,219	$ 463,661	$ 2,154,530	$ 2,044,312
Income from operations									40,239	$ (12,183)
Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Number of businesses acquired \| acquisition										4
Consideration transferred									$ 33,800	$ 94,100
Number of acquisitions completed \| acquisition									5
fbm_TwoThousandAndNineteenAcquisitionsMember [Domain]
Business Acquisition [Line Items]
Net sales									$ 25,300
Income from operations									1,700
2018 Acquisitions
Business Acquisition [Line Items]
Net sales										62,900
Income from operations										2,600
Minimum \| Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Consideration transferred									3,500	6,200
Maximum \| Series of Individually Immaterial Business Acquisitions
Business Acquisition [Line Items]
Consideration transferred									$ 11,300	$ 49,300
Louisville, Kentucky \| Associated Drywall Suppliers, Inc
Business Acquisition [Line Items]
Number of branch locations \| branch	1								1
Colorado Springs, Colorado \| Joe's Wallboard Supply
Business Acquisition [Line Items]
Number of branch locations \| branch											1	1
Lakewood, Washington \| The Supply Guy, Inc
Business Acquisition [Line Items]
Number of branch locations \| branch											1
South Dakota and Iowa \| Agan
Business Acquisition [Line Items]
Number of branch locations \| location													3
Pennsylvania and Virginia \| Ciesco
Business Acquisition [Line Items]
Number of branch locations \| location														6
Minnesota, North Dakota, South Dakota and Nebraska \| ArmCom
Business Acquisition [Line Items]
Number of branch locations \| location															5
Missouri \| RM Supply
Business Acquisition [Line Items]
Number of branch locations \| location															2