Borrowings - Post-Swap Borrowing (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Borrowings
Fixed-rate debt, Amount	$ 28,770	$ 29,007
Floating-rate debt, Amount	13,886	16,044
Long-term debt (including current maturities)	$ 42,656	$ 45,052
Fixed-rate debt, Weighted-average Interest Rate (as a percent)	2.70%	2.70%
Floating-rate debt, Weighted-average Interest Rate (as a percent)	3.00%	2.10%
Interest rate swaps \| Derivative instruments in fair value hedges
Borrowings
Notional amount	$ 7,563	$ 9,138

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
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-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Section S99
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The interest rate applicable to the portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

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The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

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The portion of the carrying amount of long-term borrowings outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time.

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