Valuation and Qualifying Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Valuation Allowances and Reserves, Beginning Balance	$ 37,998		$ 39,674		$ 52,786
Valuation Allowances and Reserves, Reserves of Businesses Acquired	5,357	[1]	5,849	[1]	1,001	[1]
Valuation Allowances and Reserves, Deductions	8,187		12,526		21,628
Valuation Allowances and Reserves, Charged to Cost and Expense	12,957		5,001		7,515
Valuation Allowances and Reserves, Ending Balance	$ 48,125		$ 37,998		$ 39,674

[1] Represents the allowance for doubtful accounts of the businesses acquired by the company during 2011, 2010, and 2009.