Selected Segment Data (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Segment Reporting Information [Line Items]
Revenues	$ 581.6	$ 691.3
Operating profit (loss):	21.7	127.2
Other operating credits and charges, net	(1.9)	0.4
Gain (loss) on sale or impairment of long-lived assets, net	(0.5)	0.6
General corporate and other expenses, net	(8.3)	(5.8)
Interest expense, net of capitalized interest	(3.8)	(4.4)
Investment income	4.7	3.2
Other non-operating items	11.0	(1.4)
Income from continuing operations before taxes	33.6	124.6
Provision for income taxes	7.2	29.7
Income from continuing operations	26.4	94.9
Siding [Member]
Segment Reporting Information [Line Items]
Revenues	235.6	227.0
Operating profit (loss):	33.1	35.9
OSB [Member]
Segment Reporting Information [Line Items]
Revenues	208.4	313.3
Operating profit (loss):	(7.7)	89.2
EWP [Member]
Segment Reporting Information [Line Items]
Revenues	90.4	105.8
Operating profit (loss):	2.5	0.3
South America [Member]
Segment Reporting Information [Line Items]
Revenues	44.6	42.4
Operating profit (loss):	8.0	8.9
Other [Member]
Segment Reporting Information [Line Items]
Revenues	4.4	2.8
Operating profit (loss):	(3.5)	(2.3)
Intersegment [Member]
Segment Reporting Information [Line Items]
Revenues	$ (1.8)	$ 0.0