Commitments and Contingencies - Additional Information (Detail) - USD ($)					12 Months Ended
	May 08, 2018	Jan. 05, 2018	Jul. 28, 2016	Jun. 16, 2016	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2014
Commitments And Contingencies [Line Items]
Letters of credit outstanding, amount					$ 7,500,000
Contingently liable for performance, current						$ 26,100,000
Outstanding guarantees						$ 0
Percentage of expected natural gas usage						25.00%
Operating leases Rental expense					12,000,000	$ 11,300,000	$ 10,300,000
USG Corporation and United States Gypsum [Member]
Commitments And Contingencies [Line Items]
Litigation settlement amount								$ 48,000,000
Temple Inland Inc. [Member]
Commitments And Contingencies [Line Items]
Litigation settlement amount								$ 7,000,000
Lafarge North America [Member] | Direct Purchaser Class [Member]
Commitments And Contingencies [Line Items]
Litigation settlement amount				$ 23,000,000
Lafarge North America [Member] | Indirect Purchaser Class [Member]
Commitments And Contingencies [Line Items]
Litigation settlement amount			$ 5,200,000
American Gypsum Company LLC [Member] | Homebuilder Settlement Agreement [Member] | Subsequent Event [Member]
Commitments And Contingencies [Line Items]
Litigation settlement amount	$ 6,000,000
American Gypsum Company LLC [Member] | Direct and Indirect Purchaser Class [Member] | Direct and Indirect Purchaser Settlement Agreements [Member]
Commitments And Contingencies [Line Items]
Litigation settlement amount		$ 39,100,000
Amount deposited to qualified settlement fund					$ 38,800,000