Selected Segment Data (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Net sales:	$ 691.3	$ 610.9
Operating profit (loss):	127.2	75.4
Other operating credits and charges, net	0.4	(3.4)
Gain (loss) on sale or impairment of long-lived assets, net	0.6	(0.6)
General corporate and other expenses, net	(27.3)	(27.8)
Interest expense, net of capitalized interest	(4.4)	(5.0)
Investment income	3.2	2.0
Other non-operating items	(1.4)	(1.9)
Income before taxes	124.6	70.5
Provision for income taxes	29.7	15.5
Income from continuing operations	94.9	55.0
Siding [Member]
Segment Reporting Information [Line Items]
Net sales:	227.0	214.0
Operating profit (loss):	45.3	40.7
OSB [Member]
Segment Reporting Information [Line Items]
Net sales:	313.3	268.4
Operating profit (loss):	97.4	60.8
EWP [Member]
Segment Reporting Information [Line Items]
Net sales:	100.7	82.1
Operating profit (loss):	2.8	0.8
South America [Member]
Segment Reporting Information [Line Items]
Net sales:	42.4	37.8
Operating profit (loss):	8.9	5.1
Other [Member]
Segment Reporting Information [Line Items]
Net sales:	7.9	8.7
Operating profit (loss):	(0.9)	(0.2)
Intersegment [Member]
Segment Reporting Information [Line Items]
Net sales:	$ 0.0	$ (0.1)