Valuation and Qualifying Accounts and Reserves (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]
Valuation and Qualifying Accounts and Reserves
Balance at Beginning of Period	$ 9,220	$ 10,620	$ 8,455
Charge to Cost and Expense	5,336	6,494	4,717
Additions Charge to other Accounts
Acquisitions and Divestitures
Charge - offs, Net of Recoveries	(2,737)	(7,894)	(2,552)
Balance at End of Period	$ 11,819	$ 9,220	$ 10,620