Fair Value Measurements (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 1,043,632,000	$ 1,012,122,000
Short-term investments	1,198,289,000	1,362,641,000
Commodity contracts	1,790,000	5,071,000
Restricted cash and investments	586,190,000	585,833,000
Total assets	2,829,901,000	2,965,667,000
Foreign exchange and commodity contracts	(113,000)	(21,434,000)
Fair value of short-term and long-term debt, including current maturities	4,750,000,000	4,760,000,000
Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	1,043,632,000	1,012,122,000
Short-term investments	1,198,289,000	1,362,641,000
Commodity contracts
Restricted cash and investments	586,190,000	585,833,000
Total assets	2,828,111,000	2,960,596,000
Foreign exchange and commodity contracts
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents
Short-term investments
Commodity contracts	1,790,000	5,071,000
Restricted cash and investments
Total assets	1,790,000	5,071,000
Foreign exchange and commodity contracts	(113,000)	(21,434,000)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents
Short-term investments
Commodity contracts
Restricted cash and investments
Total assets
Foreign exchange and commodity contracts