Borrowings (Long-term Debt Including Unamortized Debt Discounts and Premiums) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Fixed Interest Rate	5.45%
Senior Notes	$ 7,481	$ 6,881
Finance lease obligation	0	52
Unamortized discount — net	(14)	(15)
Debt issuance costs	(40)	(40)
Total long-term debt	$ 7,427	6,878
Senior Notes [Member] \| Senior Notes Due 2020 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	4.45%
Senior Notes	$ 700	700
Senior Notes [Member] \| Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	3.25%
Senior Notes	$ 600	600
Senior Notes [Member] \| Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	3.225%
Senior Notes	$ 256	256
Senior Notes [Member] \| Senior Notes Due 2023 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	2.65%
Senior Notes	$ 800	800
Senior Notes [Member] \| Senior Notes Due 2024 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	3.55%
Senior Notes	$ 500	500
Senior Notes [Member] \| Senior Notes Due 2025 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	3.00%
Senior Notes	$ 375	375
Senior Notes [Member] \| Senior Notes Due May 2025 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	3.85%
Senior Notes	$ 750	750
Senior Notes [Member] \| Senior Notes Due 2026 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	3.45%
Senior Notes	$ 350	350
Senior Notes [Member] \| Senior Notes Due 2027 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	3.20%
Senior Notes	$ 650	650
Senior Notes [Member] \| Senior Notes Due 2028 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	3.20%
Senior Notes	$ 700	700
Senior Notes [Member] \| Senior Notes Due 2029 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	4.00%
Senior Notes	$ 600	600
Senior Notes [Member] \| Senior Notes Due May 2029 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	3.25%
Senior Notes	$ 600	0
Senior Notes [Member] \| Floating Rate Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Senior Notes	$ 600	$ 600
Senior Notes [Member] \| Floating Rate Senior Notes Due 2021 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Basis spread rate	0.32%

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

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Amount of long-term debt and lease obligation, classified as noncurrent.

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