Debt - Schedule of Long-Term Debt (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term debt	$ 8,798us-gaap_LongTermDebt	$ 1,250us-gaap_LongTermDebt	$ 8,262us-gaap_LongTermDebt
Less: amount due within one year	29us-gaap_LongTermDebtCurrent		655us-gaap_LongTermDebtCurrent
Long-term debt, excluding amount due within one year	8,769us-gaap_LongTermDebtNoncurrent		7,607us-gaap_LongTermDebtNoncurrent
Long-term debt	8,798us-gaap_LongTermDebt	1,250us-gaap_LongTermDebt	8,262us-gaap_LongTermDebt
5.25% Convertible Notes Due 2014 [Member]
Debt Instrument [Line Items]
Long-term debt			575
Long-term debt			575
5.55% Notes, Due 2017 [Member]
Debt Instrument [Line Items]
Long-term debt	750		750
Long-term debt	750		750
6.50% Bonds, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	250		250
Long-term debt	250		250
6.75% Notes, Due 2018 [Member]
Debt Instrument [Line Items]
Long-term debt	750		750
Long-term debt	750		750
5.72% Notes, Due 2019 [Member]
Debt Instrument [Line Items]
Long-term debt	750		750
Long-term debt	750		750
6.150% Notes, Due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt	1,000		1,000
Long-term debt	1,000		1,000
5.40% Notes, Due 2021 [Member]
Debt Instrument [Line Items]
Long-term debt	1,250		1,250
Long-term debt	1,250		1,250
5.87% Notes, Due 2022 [Member]
Debt Instrument [Line Items]
Long-term debt	627		627
Long-term debt	627		627
5.125% Notes, Due 2024 [Member]
Debt Instrument [Line Items]
Long-term debt	1,250
Long-term debt	1,250
5.90% Notes, Due 2027 [Member]
Debt Instrument [Line Items]
Long-term debt	625		625
Long-term debt	625		625
6.75% Bonds, Due 2028 [Member]
Debt Instrument [Line Items]
Long-term debt	300		300
Long-term debt	300		300
5.95% Notes Due 2037 [Member]
Debt Instrument [Line Items]
Long-term debt	625		625
Long-term debt	625		625
BNDES Loans, Due 2015-2029 [Member]
Debt Instrument [Line Items]
Long-term debt	267		325
Long-term debt	267		325
Iowa Finance Authority Loan, Due 2042 (4.75%) [Member]
Debt Instrument [Line Items]
Long-term debt	250		250
Long-term debt	250		250
Other [Member]
Debt Instrument [Line Items]
Long-term debt	104		185
Long-term debt	$ 104		$ 185

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Carrying amount of long-term debt, net of unamortized discount or premium, including current and noncurrent amounts. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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- Definition

Amount of long-term debt, after unamortized discount or premium, scheduled to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19,20)

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- Definition

Carrying amount of long-term debt, net of unamortized discount or premium, excluding amounts to be repaid within one year or the normal operating cycle, if longer (current maturities). Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

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