Cost in Excess of Net Assets of Companies Acquired and Intangible Assets, net Cost in Excess of Net Assets of Companies Acquired and Intangible Assets, net - Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross carrying amount	$ 518,424		$ 484,331
Accumulated amortization	(104,391)		(91,568)
Intangible assets, net	414,033		392,763
Amortization of Intangible Assets	36,508		35,359		21,132
Future Amortization Expense, Year One	36,165
Future Amortization Expense, Year Two	35,584
Future Amortization Expense, Year Three	35,207
Future Amortization Expense, Year Four	33,570
Future Amortization Expense, Year Five	29,816
Customer Relationships [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted Average Useful Life	11		11
Gross carrying amount	325,509		267,729
Accumulated amortization	(100,172)		(69,762)
Intangible assets, net	225,337		197,967
Patented Technology [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted Average Useful Life	5		6
Gross carrying amount	11,154		11,029
Accumulated amortization	(2,508)		(693)
Intangible assets, net	8,646		10,336
Procurement Agreement [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Weighted Average Useful Life			5
Gross carrying amount			12,000
Accumulated amortization			(11,400)
Intangible assets, net			600
Other Intangible Assets [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross carrying amount	2,761	[1]	14,573	[1]
Accumulated amortization	(1,711)	[1]	(9,713)	[1]
Intangible assets, net	1,050	[1]	4,860	[1]
Acquired Finite-lived Intangible Asset, Useful Life, Minimum			1
Acquired Finite-lived Intangible Asset, Useful Life, Maximum			3
Trade Names [Member]
Finite And Indefinite Lived Intangible Assets [Line Items]
Gross carrying amount	179,000		179,000
Accumulated amortization	0		0
Intangible assets, net	$ 179,000		$ 179,000

[1] Consists of non-competition agreements and sales backlog with useful lives ranging from one to three years.