Acquisitions (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Oct. 13, 2010
Business Acquisition [Line Items]
Goodwill					$ 179,900,000
Sales	300,639,000	243,058,000	873,826,000	693,985,000
Net income	20,181,000	9,985,000	53,158,000	27,039,000
European Segment [Member] | General Monitors, Inc [Member]
Business Acquisition [Line Items]
Goodwill	43,200,000		43,200,000
North American Segment [Member] | General Monitors, Inc [Member]
Business Acquisition [Line Items]
Goodwill	136,700,000		136,700,000
Fair value of acquired inventory	4,800,000		4,800,000
General Monitors, Inc [Member]
Business Acquisition [Line Items]
Total acquisition price of General Monitors, Inc.					278,200,000
Contingent considerations					0
Escrow deposit, amount					38,000,000
Expiration date of escrow agreement, in years					two
Acquisition price					264,000,000
Revolving credit facility for borrowings					250,000,000
Weighted-average amortization period of identifiable intangible assets acquired, in years			16
Identifiable intangible assets, future amortization expense			3,300,000
Sales	22,200,000		63,500,000
Net income	4,800,000		11,200,000
Net income including one-time increase in cost of sales			2,300,000
Net income including one-time increase in cost of sales, after tax			1,500,000
Future Amortization Expense, Year One			3,300,000
Future Amortization Expense, Year Two			3,300,000
Future Amortization Expense, Year Three			3,300,000
Future Amortization Expense, Year Four			3,300,000
Future Amortization Expense, Year Five			3,300,000
General Monitors, Inc [Member] | 4.00% Series A Senior Notes [Member]
Business Acquisition [Line Items]
Issuance of senior notes					100,000,000
Senior Notes, interest percentage					4.00%
Senior Notes, maturity date			October 13, 2021
Senior notes, number of annual installments			five
Senior notes, annual principal payment	$ 20,000,000		$ 20,000,000