Segment Information Identifiable assets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Assets	$ 2,448.5	$ 2,031.2
OSB
Assets	577.5	555.0
Siding
Assets	371.8	344.1
Engineered Wood Products
Assets	116.3	115.6
South America
Assets	95.9	85.5
Other
Assets	93.7	75.9
Unallocated Amount to Segment
Assets	$ 1,193.3	$ 855.1

Sum of the carrying amounts as of the balance sheet date of all assets that are recognized. Assets are probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(12))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(11))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Name:	us-gaap_Assets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant