Debt (Long-Term Debt) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Long-Term Debt
Unamortized discount for the Notes above	$ (42)	$ (50)
Subtotal	3,958	3,950
Total future finance lease payments		62
Total future finance lease payments	685
Less: imputed interest for finance leases	(89)
Total long-term debt	4,554	4,012
3.625% Notes due on May 19, 2021
Long-Term Debt
Long-term debt	$ 1,000	1,000
Long-term debt, stated interest rate	3.625%
3.375% Notes due on February 25, 2024
Long-Term Debt
Long-term debt	$ 1,000	1,000
Long-term debt, stated interest rate	3.375%
1.998% Notes due on August 15, 2026
Long-Term Debt
Long-term debt	$ 2,000	$ 2,000
Long-term debt, stated interest rate	1.998%

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 and due to be paid more than one year (or one operating cycle, if longer) after the balance sheet date.

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