Fair Value Measurements (Detail) (USD $)	Jun. 30, 2012	Dec. 31, 2011
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Cash equivalents	$ 988,698,000	$ 1,012,122,000
Short-term investments	569,421,000	1,362,641,000
Commodity contracts	488,000	5,071,000
Restricted cash and investments	491,640,000	585,833,000
Total assets	2,050,247,000	2,965,667,000
Foreign exchange and commodity contracts	(52,000)	(21,434,000)
Fair value of short-term and long-term debt, including current maturities	4,850,000,000	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	988,698,000	1,012,122,000
Short-term investments	569,421,000	1,362,641,000
Restricted cash and investments	491,640,000	585,833,000
Total assets	2,049,759,000	2,960,596,000
Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Commodity contracts	488,000	5,071,000
Total assets	488,000	5,071,000
Foreign exchange and commodity contracts	$ (52,000)	$ (21,434,000)