Goodwill and Intangible Assets, net (Schedule of Goodwill and Other Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Goodwill	$ 625,357	$ 575,705
Less - accumulated amortization	(5,425)	(5,425)
Goodwill, net	619,932	570,280	561,002
Intangible assets, at cost	125,268	117,582
Less - accumulated amortization	(109,145)	(100,757)
Intangible assets, net	16,123	16,825
Goodwill and intangible assets, net	636,055	587,105
Customer Lists and Relationships [Member]
Customer lists and relationships	78,462	72,679
Intangible assets, net	12,329
Non-compete Agreements [Member]
Non-compete agreements	22,236	21,002
Intangible assets, net	1,615
Other [Member]
Other	24,570	23,901
Intangible assets, net	$ 2,179