Principal Accounting Policies (Schedule Of Allowance For Revenue Adjustments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Accounting Policies [Abstract]
Balance at beginning of period	$ 16,920	$ 14,291	$ 14,454
Additions Charged to expense	0	0	0
Additions Charged to other accounts - Revenue	77,310	86,853	85,272
Write-offs	(80,414)	(84,224)	(85,435)
Balance at end of period	$ 13,816	$ 16,920	$ 14,291