Segment Information Additional Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			12 Months Ended			3 Months Ended		12 Months Ended
	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Mar. 31, 2012 OSB Mills Construction Related Legal Reserves [Member]	Sep. 30, 2011 OSB Mills Construction Related Legal Reserves [Member]	Dec. 31, 2011 OSB Mills Construction Related Legal Reserves [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2011 Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2010 Fair Value, Inputs, Level 2 [Member]	Dec. 31, 2012 Supplemental Employee Retirement Plans, Defined Benefit [Member]	Dec. 31, 2012 Siding [Member]
Segment Reporting Information [Line Items]
Severance Costs				$ 0.5	$ 1.1	$ 0	$ 0.3	$ (0.4)	$ (1.1)
Loss Contingency Accrual, Carrying Value, Provision							0.5
Product Warranty Accrual, Period Increase (Decrease)				(1.8)	(0.4)	0								1.0
Impairment of Long-Lived Assets to be Disposed of										4.4	6.9
Gain on settlement of litigation related to ARS			0.8	20.0	0	0
Adjustments related to prior year inventory				1.5	0	0
Adjustments to retirement accounts				3.8	0	0
Defined Benefit Plan, Recognized Net Gain (Loss) Due to Curtailments				2.2	0	0.2							2.2
Other Postretirement Benefit Expense				1.6
Reductions, net of additions, to product related contingency reserves	(10.7)			(5.0)	(11.5)	(2.5)
Reserves For Timber Obligations		1.5		0.8	1.5	0
Accrual for Environmental Loss Contingencies, Provision for New Losses		0.9		0	(0.9)	0
Other-than-temporary impairment of investments				$ 0	$ 14.8	$ 17.0						$ 17.0