Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Balance Sheet) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Current assets	$ 132,290	$ 120,397
Property and equipment, net	1,485,319	1,310,514
Other assets	81,920	96,769
Total assets	1,699,529	1,527,680
Current liabilities	287,452	271,320
Long-term liabilities	888,991	746,505
Shareholders' equity	523,086	509,855
Total liabilities and shareholders' equity	1,699,529	1,527,680
Parent Company [Member]
Current assets	1,482,390	1,349,841
Property and equipment, net	129,459	101,015
Investment in subsidiaries	(41,003)	(58,764)
Other assets	27,634	38,853
Total assets	1,598,480	1,430,945
Current liabilities	172,047	150,793
Long-term liabilities	853,824	724,801
Shareholders' equity	572,609	555,351
Total liabilities and shareholders' equity	1,598,480	1,430,945
Combined Guarantor Subsidiaries [Member]
Current assets	95,939	71,018
Property and equipment, net	1,266,215	1,131,672
Other assets	45,767	54,062
Total assets	1,407,921	1,256,752
Current liabilities	1,504,038	1,368,456
Long-term liabilities	2,362	2,183
Shareholders' equity	(98,479)	(113,887)
Total liabilities and shareholders' equity	1,407,921	1,256,752
Combined Non-Guarantor Subsidiaries [Member]
Current assets	2,047	3,874
Property and equipment, net	81,841	68,911
Other assets	10,149	9,133
Total assets	94,037	81,918
Current liabilities	3,754	4,366
Long-term liabilities	32,805	22,429
Shareholders' equity	57,478	55,123
Total liabilities and shareholders' equity	94,037	81,918
Eliminations [Member]
Current assets	(1,448,086)	(1,304,336)
Property and equipment, net	7,804	8,916
Investment in subsidiaries	41,003	58,764
Other assets	(1,630)	(5,279)
Total assets	(1,400,909)	(1,241,935)
Current liabilities	(1,392,387)	(1,252,295)
Long-term liabilities		(2,908)
Shareholders' equity	(8,522)	13,268
Total liabilities and shareholders' equity	$ (1,400,909)	$ (1,241,935)