Business Combinations (Summary Of Unaudited Pro Forma) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Business Combinations [Abstract]
Revenues	$ 1,228,756,000	$ 1,198,673,000	$ 985,528,000	$ 872,938,000	$ 835,394,000	$ 874,705,000	$ 764,295,000	$ 711,874,000	$ 4,285,895,000	$ 3,186,268,000	$ 2,576,081,000
Total revenues pro forma									4,825,600,000	4,299,900,000
Income (loss) before income taxes									135,251,000	177,108,000	25,404,000
Income (loss) before income taxes pro forma									$ 113,500,000	$ (1,200,000)