Intangible Assets and Goodwill (Details) (USD $)	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2012 Customer Relationships [Member]	Dec. 31, 2011 Customer Relationships [Member]	Mar. 31, 2012 Supplier Relationships [Member]	Dec. 31, 2011 Supplier Relationships [Member]	Mar. 31, 2012 Software And Technology [Member]	Dec. 31, 2011 Software And Technology [Member]	Mar. 31, 2012 Trademark And Trade Name [Member]	Dec. 31, 2011 Trademark And Trade Name [Member]	Mar. 31, 2012 Noncompete Agreements [Member]	Dec. 31, 2011 Noncompete Agreements [Member]	Mar. 31, 2012 Total Intangible Assets [Member]	Dec. 31, 2011 Total Intangible Assets [Member]
Finite lived intangible assets
Finite lived intangible assets, gross			$ 412,020,000	$ 409,489,000	$ 29,000,000	$ 29,000,000	$ 171,519,000	$ 170,286,000	$ 34,299,000	$ 33,908,000	$ 7,596,000	$ 7,564,000	$ 654,434,000	$ 650,247,000
Finite lived intangible assets accumulated amortization			(247,106,000)	(237,536,000)	(19,938,000)	(19,213,000)	(147,071,000)	(143,456,000)	(30,953,000)	(30,076,000)	(7,475,000)	(7,363,000)	(452,543,000)	(437,644,000)
Finite lived intangible assets, net			164,914,000	171,953,000	9,062,000	9,787,000	24,448,000	26,830,000	3,346,000	3,832,000	121,000	201,000	201,891,000	212,603,000
Finite Lived Intangible Assets Amortization Expense	$ 12,000,000	$ 15,000,000