Operations and Summary of Significant Accounting Policies (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 segment month	Dec. 31, 2010	Dec. 31, 2009
Operations and Summary of Significant Accounting Policies
High end of the range of the required percentage voting interest held to account for investments with the equity method of accounting	50.00%
Original or remaining maturity period of investment classified as cash or cash equivalent (in months)	3
Allowance for Doubtful Accounts
Percentage reserved for accounts receivable due from customers in deteriorating financial condition	100.00%
Fair value of financial instruments
United States Treasury securities and money market funds included in cash equivalents	$ 53.3
Product Research and Development Costs
Product Research and Development Costs	6.1	6.5	5.9
Selling Costs
Advertising expenses	$ 6.3	$ 5.4	$ 5.3
Segments and Discontinued Operations
Number of reportable segments prior to the sale of Simpson Dura-Vent Company, Inc.	2
Number of reportable segments	3
Maximum
Revenue Recognition
Service sales as a percentage of net sales	1.00%
Software
Property, Plant and Equipment
Estimated useful life, minimum (in years)	3
Estimated useful life, maximum (in years)	5
Machinery and equipment
Property, Plant and Equipment
Estimated useful life, minimum (in years)	3
Estimated useful life, maximum (in years)	10
Buildings and site improvements
Property, Plant and Equipment
Estimated useful life, minimum (in years)	15
Estimated useful life, maximum (in years)	45