Revenue - Schedule of Disaggregation of Revenue by Product Classification (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation Of Revenue [Line Items]
Net Sales	$ 245.3	$ 212.7	$ 707.4	$ 607.7
ASC Topic 606 [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	245.3	212.7	707.4	607.7
ASC Topic 606 [Member] | Millwork Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	105.7	90.8	299.2	268.7
ASC Topic 606 [Member] | Building Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	119.6	106.1	347.6	296.1
ASC Topic 606 [Member] | Wood Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	$ 20.0	$ 15.8	$ 60.6	$ 42.9