Revenue - Schedule of Disaggregation of Revenue by Product Classification (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation Of Revenue [Line Items]
Net Sales	$ 792.3	$ 812.0	$ 839.6
ASC Topic 606
Disaggregation Of Revenue [Line Items]
Net Sales	792.3	812.0	839.6
ASC Topic 606 | Millwork [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	357.0	384.6	400.6
ASC Topic 606 | Building Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	379.0	366.6	365.4
ASC Topic 606 | Wood Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	$ 56.3	$ 60.8	$ 73.6