Property and Equipment (Details) (USD $)	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2012	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Plant and equipment
Property and equipment		$ 3,601,365,000		$ 3,601,365,000		$ 3,372,277,000
Less accumulated depreciation		(1,181,278,000)		(1,181,278,000)		(1,095,077,000)
Property and equipment, net		2,420,087,000		2,420,087,000		2,277,200,000
Increase in property and equipment primarily due to acquisition	229,100,000
Depreciation expense		56,700,000	53,400,000	109,900,000	105,800,000
Interest capitalized in connection with major construction projects		3,000,000	1,000,000	5,900,000	1,800,000
Land and improvements
Plant and equipment
Property and equipment		372,633,000		372,633,000		362,402,000
Building and improvements
Plant and equipment
Property and equipment		1,854,582,000		1,854,582,000		1,715,144,000
Furniture, fixtures and equipment
Plant and equipment
Property and equipment		1,149,001,000		1,149,001,000		1,021,362,000
Leasehold improvements
Plant and equipment
Property and equipment		16,910,000		16,910,000		16,910,000
Construction in progress
Plant and equipment
Property and equipment		$ 208,239,000		$ 208,239,000		$ 256,459,000