Intangible Assets and Goodwill (Details) (USD $)	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Customer Relationships [Member]	Dec. 31, 2012 Customer Relationships [Member]	Mar. 31, 2013 Supplier Relationships [Member]	Dec. 31, 2012 Supplier Relationships [Member]	Mar. 31, 2013 Software And Technology [Member]	Dec. 31, 2012 Software And Technology [Member]	Mar. 31, 2013 Trademark And Trade Name [Member]	Dec. 31, 2012 Trademark And Trade Name [Member]	Mar. 31, 2013 Noncompete Agreements [Member]	Dec. 31, 2012 Noncompete Agreements [Member]	Mar. 31, 2013 Total Intangible Assets [Member]	Dec. 31, 2012 Total Intangible Assets [Member]
Finite lived intangible assets
Finite lived intangible assets, gross			$ 403,534,000	$ 407,901,000	$ 29,000,000	$ 29,000,000	$ 167,873,000	$ 169,632,000	$ 34,554,000	$ 35,078,000	$ 7,372,000	$ 7,471,000	$ 642,333,000	$ 649,082,000
Finite lived intangible assets accumulated amortization			(274,203,000)	(269,100,000)	(22,838,000)	(22,113,000)	(152,074,000)	(151,628,000)	(32,450,000)	(32,615,000)	(7,328,000)	(7,412,000)	(488,893,000)	(482,868,000)
Finite lived intangible assets, net	153,440,000		129,331,000	138,801,000	6,162,000	6,887,000	15,799,000	18,004,000	2,104,000	2,463,000	44,000	59,000	153,440,000	166,214,000
Finite Lived Intangible Assets Amortization Expense	$ 10,000,000	$ 12,000,000