Valuation Allowances and Reserves (details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2008
Valuation and Qualifying Accounts [Abstract]
Allowance For Doubtful Accounts Receivable Current	$ 2,895	$ 2,950	$ 3,125	$ 2,927
Valuation Allowances and Reserves, Charged to Cost and Expense	1,919	1,717	4,201
Valuation Allowances and Reserves, Deductions	1,974	1,892	4,003
Valuation Allowances and Reserves, Charged to Other Accounts	$ 0	$ 0	$ 0