Summary Of Significant Accounting Policies (Allowance For Doubtful Accounts) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Summary Of Significant Accounting Policies [Abstract]
Allowance as of the beginning of the year	$ 44,883	$ 42,928	$ 45,062
Additions expensed during the year	5,232	5,194	5,344
Net deductions	(6,157)	(3,239)	(7,478)
Allowance as of the end of the year	$ 43,958	$ 44,883	$ 42,928