Schedule II - 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]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 10,154	$ 9,484	$ 9,167
Charged to Costs and Expenses	478	633	1,047
Write-off of Doubtful Accounts	104	(37)	730
Balance at End of Period	$ 10,528	$ 10,154	$ 9,484