Debt and Credit Facilities Summary of Debt Carrying Amount (Details) - USD ($) $ in Millions	3 Months Ended
Sep. 30, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Short-term and long-term debt	$ 24,588	$ 27,322
Long-term Debt, Current Maturities	2,498	2,748
Total long-term debt, net	22,090	24,574
Unsecured Debt \| 2017 Senior Unsecured Notes Due in March 2019
Debt Instrument [Line Items]
Long-term debt	$ 0	750
Unsecured Debt \| Senior Unsecured Notes Due in April 2019
Debt Instrument [Line Items]
Interest Rate	2.05%
Long-term debt	$ 0	500
Unsecured Debt \| 2017 Senior Unsecured Notes Due in September 2019 with Fixed Rate
Debt Instrument [Line Items]
Interest Rate	1.85%
Long-term debt	$ 0	999
Unsecured Debt \| 2017 Senior Unsecured Notes Due in September 2019 with Floating Rate
Debt Instrument [Line Items]
Long-term debt	$ 0	499
Unsecured Debt \| Senior Unsecured Notes Due In February 2020
Debt Instrument [Line Items]
Interest Rate	2.35%
Long-term debt	$ 500	499
Unsecured Debt \| Senior Unsecured Notes Due in September 2020
Debt Instrument [Line Items]
Interest Rate	2.55%
Long-term debt	$ 1,998	1,996
Unsecured Debt \| Senior Unsecured Notes Due in April 2021
Debt Instrument [Line Items]
Interest Rate	4.50%
Long-term debt	$ 998	997
Unsecured Debt \| Senior Unsecured Notes Due In December 2021
Debt Instrument [Line Items]
Interest Rate	4.40%
Long-term debt	$ 1,248	1,247
Unsecured Debt \| Senior Unsecured Notes Due in March 2022
Debt Instrument [Line Items]
Interest Rate	1.95%
Long-term debt	$ 498	498
Unsecured Debt \| Senior Unsecured Notes Due in September 2022
Debt Instrument [Line Items]
Interest Rate	3.25%
Long-term debt	$ 998	997
Unsecured Debt \| Senior Unsecured Notes Due in September 2023
Debt Instrument [Line Items]
Interest Rate	2.50%
Long-term debt	$ 746	746
Unsecured Debt \| Senior Unsecured Notes Due in April 2024
Debt Instrument [Line Items]
Interest Rate	3.70%
Long-term debt	$ 1,745	1,744
Unsecured Debt \| Senior Unsecured Notes Due in February 2025
Debt Instrument [Line Items]
Interest Rate	3.50%
Long-term debt	$ 1,745	1,745
Unsecured Debt \| Senior Unsecured Notes Due in March 2026
Debt Instrument [Line Items]
Interest Rate	3.65%
Long-term debt	$ 2,733	2,731
Unsecured Debt \| Senior Unsecured Notes Due in March 2027
Debt Instrument [Line Items]
Interest Rate	2.95%
Long-term debt	$ 1,245	1,245
Unsecured Debt \| Senior Unsecured Notes Due in September 2035
Debt Instrument [Line Items]
Interest Rate	4.60%
Long-term debt	$ 991	990
Unsecured Debt \| Senior Unsecured Notes Due in September 2036
Debt Instrument [Line Items]
Interest Rate	4.00%
Long-term debt	$ 741	740
Unsecured Debt \| Senior Unsecured Notes Due in December 2041
Debt Instrument [Line Items]
Interest Rate	5.65%
Long-term debt	$ 995	995
Unsecured Debt \| Senior Unsecured Notes Due in April 2044
Debt Instrument [Line Items]
Interest Rate	4.80%
Long-term debt	$ 1,734	1,734
Unsecured Debt \| Senior Unsecured Notes Due in February 2045
Debt Instrument [Line Items]
Interest Rate	4.50%
Long-term debt	$ 1,731	1,730
Unsecured Debt \| Senior Unsecured Notes Due in March 2046
Debt Instrument [Line Items]
Interest Rate	4.75%
Long-term debt	$ 2,217	2,216
Unsecured Debt \| Senior Unsecured Notes Due in March 2047
Debt Instrument [Line Items]
Interest Rate	4.15%
Long-term debt	$ 1,725	$ 1,724
London Interbank Offered Rate (LIBOR) \| 2017 Senior Unsecured Notes Due in September 2019 with Floating Rate
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.25%
London Interbank Offered Rate (LIBOR) \| 2017 Senior Unsecured Notes Due in March 2019
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.22%

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

No definition available.

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

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- Definition

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

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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