Accounts payable and accrued expenses related to payable to equity method investee.

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Additional cash to offset purchase price adjustments.

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Business combination adjustment to cash consideration.

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Number of manufacturing facility.

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Payment made to investment in joint venture from proceeds from sale of business.

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Potential adjustments to the purchase price consideration.

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Revised maximum potential adjustment to purchase price consideration.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

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-Name Accounting Standards Codification
-Topic 230
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-Section 45
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Dividends received on equity and other investments during the current period.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Business (Narrative) (Details) $ in Millions								3 Months Ended	12 Months Ended
Business (Narrative) (Details) $ in Millions	Nov. 25, 2019 Facility	Mar. 04, 2019 Facility	Aug. 16, 2018 Facility	Jul. 18, 2018 USD ($)	May 31, 2018 Facility	Nov. 17, 2017 USD ($)	Jan. 13, 2017 Facility	Sep. 30, 2018 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2019
Business And Basis Of Presentation [Line Items]
Consideration received in connection with sale of businesses										$ 330.0
Payment to WAVE from Knauf proceeds										70.0
Maximum [Member]
Business And Basis Of Presentation [Line Items]
Potential adjustments to the purchase price consideration						$ 35.0
Potential adjustments to the purchase price consideration				$ 20.0
Knauf [Member]
Business And Basis Of Presentation [Line Items]
Business acquisition, cash consideration adjustments									$ 61.0
Knauf [Member] \| August 1, 2018 [Member]
Business And Basis Of Presentation [Line Items]
Consideration received in connection with sale of businesses				250.0
Knauf [Member] \| September 15, 2018 [Member]
Business And Basis Of Presentation [Line Items]
Consideration received in connection with sale of businesses				$ 80.0
EMEA and Pacific Rim Business [Member]
Business And Basis Of Presentation [Line Items]
Consideration received in connection with sale of businesses								$ 330.0
MRK Industries, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility \| Facility	1
Architectural Components Group, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility \| Facility		1
Steel Ceilings, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility \| Facility			1
Plasterform, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility \| Facility					1
Tectum, Inc. [Member]
Business And Basis Of Presentation [Line Items]
Number of manufacturing facility \| Facility							2
WAVE [Member]
Business And Basis Of Presentation [Line Items]
Equity interest percentage									50.00%		50.00%
Payment to WAVE from Knauf proceeds								$ 70.0
Accounts payable and accrued expenses related to payable to equity method investee									$ 25.9
WAVE [Member] \| Knauf [Member]
Business And Basis Of Presentation [Line Items]
Additional cash to offset purchase price adjustments									$ 13.1
WAVE [Member] \| Worthington [Member]
Business And Basis Of Presentation [Line Items]
Dividend received from joint venture										$ 35.0