Valuation And Qualifying Accounts (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Allowance For Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	$ 11,301		$ 10,137		$ 10,380
Charged to costs and expenses	7,157		7,563		6,105
Deductions	6,331	[1]	6,399	[1]	6,348	[1]
Balance at end of period	12,127		11,301		10,137
Tax Valuation Allowance [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at beginning of period	24,595		15,818		9,605
Charged to costs and expenses	3,781		10,823		8,570
Deductions	0	[1]	2,046	[1]	2,357	[1]
Balance at end of period	$ 28,376		$ 24,595		$ 15,818

[1] Write-offs of amounts previously reserved.