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]
Valuation and Qualifying Accounts Disclosure [Line Items]
Valuation Allowances and Reserves, Balance, Beginning Balance	$ 18,844	$ 13,070	$ 12,375
Valuation Allowances and Reserves, Charged to Cost and Expense	20,340	18,501	17,211
Valuation Allowances and Reserves, Reserves of Businesses Acquired	4,561	3,967	448
Valuation Allowances and Reserves, Deductions	(21,366)	(16,694)	(16,964)
Valuation Allowances and Reserves, Balance, Ending Balance	$ 22,379	$ 18,844	$ 13,070