Borrowings (Long-term Debt Including Unamortized Debt Discounts and Premiums) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Borrowings [Abstract]
Senior Notes	$ 2,565us-gaap_SeniorNotes	$ 1,567us-gaap_SeniorNotes
Senior Medium-Term Notes, Series A	249us-gaap_MediumTermNotes	249us-gaap_MediumTermNotes
Finance lease obligation	81us-gaap_CapitalLeaseObligations	83us-gaap_CapitalLeaseObligations
Total long-term debt	$ 2,895	$ 1,899

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

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Including the current and noncurrent portions, carrying value at the balance sheet date of a financial instrument used to receive debt funding on a regular basis with original maturities ranging from 5-10 years.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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