Long-Term Debt (Details) - USD ($) $ in Millions	Jun. 30, 2015	Feb. 28, 2015	Sep. 30, 2014
Debt Instrument [Line Items]
Capital lease obligation	$ 21		$ 26
Long-term debt and capital lease obligations	1,097		972
Less: current maturities	(18)		(7)
Long-term debt	1,079		965
4.625 percent convertible notes due 2026 \| Convertible Notes Payable
Debt Instrument [Line Items]
Debt	$ 55		$ 55
Interest rate	4.625%		4.625%
4.0 percent convertible notes due 2027 \| Convertible Notes Payable
Debt Instrument [Line Items]
Debt	$ 143		$ 162
Interest rate	4.00%	4.00%	4.00%
7.875 percent convertible notes due 2026 (net of issuance discount of $13 and $21, respectively) \| Convertible Notes Payable
Debt Instrument [Line Items]
Debt	$ 152		$ 229
Unamortized discount	$ (13)		$ (21)
Interest rate	7.875%		7.875%
6.75 percent notes due 2021
Debt Instrument [Line Items]
Debt	$ 275		$ 275
Interest rate	6.75%		6.75%
6.25 percent notes due 2024
Debt Instrument [Line Items]
Debt	$ 450		$ 225
Interest rate	6.25%		6.25%
Export financing arrangements
Debt Instrument [Line Items]
Debt	$ 23		$ 31
Unamortized discount on convertible notes
Debt Instrument [Line Items]
Unamortized discount	$ (22)		$ (31)

Amount equal to the present value (the principal) at the beginning of the lease term of minimum lease payments during the lease term (excluding that portion of the payments representing executory costs such as insurance, maintenance, and taxes to be paid by the lessor, together with any profit thereon) net of payments or other amounts applied to the principal through the balance sheet date.

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Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

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Contractual interest rate for funds borrowed, under the debt agreement.

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The amount of debt discount that was originally recognized at the issuance of the instrument that has yet to be amortized.

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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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Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

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