Accounts Receivable, Net Of Allowance (Schedule Of Allowance For Doubtful Accounts) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accounts Receivable, Net Of Allowance [Abstract]
Allowance for doubtful accounts at beginning of year	$ 8,500,000	$ 10,300,000
Provision for doubtful accounts	2,016,000	2,895,000	2,414,000
Amounts charged against the allowance	(2,800,000)	(4,700,000)
Allowance for doubtful accounts at end of year	$ 7,700,000	$ 8,500,000	$ 10,300,000