Borrowings (Long-term Debt Including Unamortized Debt Discounts and Premiums) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Senior Notes	$ 5,781	$ 4,731
Unamortized discount — net	(13)	(14)
Debt issuance costs	(33)	(25)
Total long-term debt	$ 5,790	4,753
Lease term	20 years
Senior Notes [Member] \| Senior Notes Due March 2018 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	1.50%
Senior Notes	$ 0	625
Senior Notes [Member] \| Senior Notes Due July 2018 [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	2.20%
Senior Notes	$ 0	275
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	0
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 March 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	0
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] \| Floating Rate Senior Notes Due 2021 [Member]
Debt Instrument [Line Items]
Senior Notes	$ 600	0
Senior Notes [Member] \| Floating Rate Senior Notes Due 2021 [Member] \| LIBOR [Member]
Debt Instrument [Line Items]
Basis spread rate	0.32%
Finance lease obligation [Member]
Debt Instrument [Line Items]
Fixed Interest Rate	5.45%
Finance lease obligation	$ 55	$ 61

Capital Lease Obligations, Term

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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.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

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

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Amount, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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- Definition

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 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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