SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) (Allowance for doubtful accounts, USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Allowance for doubtful accounts
Movement in valuation and qualifying accounts
Balance at Beginning of Period	$ 12,575	$ 12,550	$ 10,945
Charged to costs and expenses	504	2,236	3,683
Deductions	(3,117)	(2,211)	(2,078)
Balance at End of Period	$ 9,962	$ 12,575	$ 12,550