Revenue - Schedule of Disaggregation of Revenue by Product Classification (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation Of Revenue [Line Items]
Net Sales	$ 222.0	$ 199.6	$ 643.4	$ 574.0
ASC Topic 606
Disaggregation Of Revenue [Line Items]
Net Sales	222.0	199.6	643.4	574.0
ASC Topic 606 \| Millwork Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	104.8	97.6	303.5	288.8
ASC Topic 606 \| Building Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	96.9	82.6	281.9	229.6
ASC Topic 606 \| Wood Products [Member]
Disaggregation Of Revenue [Line Items]
Net Sales	$ 20.3	$ 19.4	$ 58.0	$ 55.6

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130543-203045

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130539-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130545-203045

Name:	us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration