Principal Accounting Policies (Schedule Of Allowance For Uncollectible Accounts) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Accounting Policies [Abstract]
Balance at beginning of period	$ 9,774	$ 6,951	$ 6,209
Additions Charged to expense	6,908	6,358	6,761
Additions Charged to other accounts	0	0	0
Write-offs net of recoveries	(10,579)	(3,535)	(6,019)
Balance at end of period	$ 6,103	$ 9,774	$ 6,951