Valuation And Qualifying Accounts (Schedule Of Valuation And Qualifying Accounts) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Allowance For Doubtful Accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	$ 9,391	$ 6,866	$ 6,050
Charged to costs and expenses	1,148	3,294	2,602
Deductions from reserves	3,496	769	1,786
Balance at end of year	7,043	9,391	6,866
Income Tax Valuation Allowance [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at beginning of year	4,323	3,174	2,973
Charged to costs and expenses		1,149	201
Deductions from reserves	1,546
Balance at end of year	$ 2,777	$ 4,323	$ 3,174