Revenue - Schedule of Disaggregation of Revenue by Product Classification (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation Of Revenue [Line Items]
Net Sales	$ 192.0	$ 218.5	$ 395.0	$ 415.9
ASC Topic 606
Disaggregation Of Revenue [Line Items]
Net Sales	192.0	218.5	395.0	415.9
ASC Topic 606 | Millwork Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	81.7	99.5	177.9	194.8
ASC Topic 606 | Building Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	97.5	101.1	190.0	189.3
ASC Topic 606 | Wood Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	$ 12.8	$ 17.9	$ 27.1	$ 31.8