Acquisitions (Details) (USD $)	12 Months Ended			12 Months Ended
	Dec. 31, 2013	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2013 2013 item	Dec. 31, 2013 2013 Minimum	Dec. 31, 2013 2013 Maximum	Dec. 31, 2012 2012 item	Dec. 31, 2012 2012 Minimum	Dec. 31, 2012 2012 Maximum
Acquisitions
Number of acquisitions completed				11			10
Notes issued				$ 1,100,000			$ 2,400,000
Net settlement of seller obligations	1,240,000	2,706,000		1,200,000
Aggregate purchase price allocation
Accounts receivable				1,076,000
Property and equipment				1,068,000			415,000
Other intangible assets				19,563,000			13,065,000
Goodwill	308,350,000	267,697,000	288,265,000	20,077,000			19,389,000
Prepaid expenses and other current assets				324,000			200,000
Liabilities				(440,000)			(5,000)
Aggregate purchase price				41,668,000			33,064,000
Period over which all intangible assets will be amortized					2 years	20 years		2 years	20 years
Expected deductible goodwill
The amount of goodwill expected to be deductible for tax purposes				$ 20,100,000			$ 19,400,000