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Other Noncurrent Assets - Schedule of Other Noncurrent Assets (Detail) (USD $)
In Millions, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Other Noncurrent Assets [Line Items]    
Intangibles, net (E) $ 407 $ 481
Cash surrender value of life insurance 464 455
Value-added tax receivable 408 510
Fair value of derivative contracts (X) 364 44
Prepaid gas transmission contract (N) 363 346
Deferred mining costs, net 223 221
Prepaid pension benefit (W) 86 109
Unamortized debt expense 86 98
Assets held for sale (B) 2 243
Other 309 289
Other assets, noncurrent, total $ 2,712 $ 2,796