Segments (Details) (USD $) In Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Selected financial information by reportable operating segment
Revenues	$ 620,593	$ 539,369	$ 1,103,729	$ 1,056,000
Adjusted EBITDA	149,791	125,116	252,497	246,897
Capital Expenditures	49,533	37,443	85,302	56,960
U.S. [Member]
Selected financial information by reportable operating segment
Revenues	444,479	410,964	775,345	799,579
Adjusted EBITDA	110,015	96,548	178,806	185,953
Capital Expenditures	27,977	23,508	39,445	36,008
International [Member]
Selected financial information by reportable operating segment
Revenues	178,720	129,641	333,191	258,912
Adjusted EBITDA	39,776	28,568	73,691	60,944
Capital Expenditures	21,556	13,935	45,857	20,952
Eliminations [Member]
Selected financial information by reportable operating segment
Revenues	$ (2,606)	$ (1,236)	$ (4,807)	$ (2,491)