Valuation and Qualifying Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Allowance for Doubtful Accounts [Member]
Balance at Beginning of Year	$ 14,973		$ 17,148		$ 19,797
Charged to Expenses	6,329		6,910		8,211
Deductions	(5,927)	[1]	(9,085)	[1]	(10,860)	[1]
Balance at End of Year	$ 15,375		$ 14,973		$ 17,148

[1] Represents write-offs