Segment Information (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Revenues Generated in Domestic and Foreign Country
Total revenues	$ 483,712	$ 404,883	$ 868,698	$ 771,298
Domestic Country [Member]
Revenues Generated in Domestic and Foreign Country
Total revenues	451,165	372,482	812,844	719,160
Foreign Country [Member]
Revenues Generated in Domestic and Foreign Country
Total revenues	$ 32,547	$ 32,401	$ 55,854	$ 52,138