Principal Accounting Policies (Schedule Of Allowance For Revenue Adjustments) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Principal Accounting Policies [Abstract]
Balance at beginning of period	$ 14,291	$ 14,454	$ 13,758
Additions Charged to expense
Additions Charged to other accounts - Revenue	86,853	85,272	83,122
Write-offs	(84,224)	(85,435)	(82,426)
Balance at end of period	$ 16,920	$ 14,291	$ 14,454