Acquisitions (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Oct. 13, 2010
Business Acquisition [Line Items]
Goodwill				$ 179,900,000
Transaction and integration costs		6,500,000
Transaction and integration costs, after tax		4,000,000
Sales	1,178,608,000	982,668,000	915,851,000
Net income	70,045,000	39,059,000	43,337,000
General Monitors, Inc. [Member]
Business Acquisition [Line Items]
Total acquisition price of General Monitors, Inc.				278,200,000
Contingent consideration				0
Escrow deposit, amount				38,000,000
Expiration date of escrow agreement, in years				two
Acquisition price				264,000,000
Issuance of Senior Notes				264,000,000
Weighted-average amortization period of identifiable intangible assets acquired, in years	16
Identifiable intangible assets, future amortization expense	3,300,000
Estimated future amortization expense of identifiable intangible assets, in year one	3,300,000
Estimated future amortization expense of identifiable intangible assets, in year two	3,300,000
Estimated future amortization expense of identifiable intangible assets, in year three	3,300,000
Estimated future amortization expense of identifiable intangible assets, in year four	3,300,000
Estimated future amortization expense of identifiable intangible assets, in year five	3,300,000
Sales	86,200,000	16,300,000
Net income	16,100,000	200,000
One-time increase in cost of sales	2,300,000	2,500,000
One-time increase in cost of sales, after tax	1,500,000	1,500,000
General Monitors, Inc. [Member] | North American Segment [Member]
Business Acquisition [Line Items]
Goodwill	136,700,000
Step up to fair value of acquired inventory	4,800,000
General Monitors, Inc. [Member] | European Segment [Member]
Business Acquisition [Line Items]
Goodwill	43,200,000
General Monitors, Inc. [Member] | 4.00% Series A Senior Notes [Member]
Business Acquisition [Line Items]
Acquisition price				100,000,000
Issuance of Senior Notes				100,000,000
Senior Notes, interest rate				4.00%
Senior Notes, maturity date	Oct. 13, 2021
Senior Notes, number of annual installments	5
Senior Notes, annual installments payable	$ 20,000,000