Debt and Credit Agreements - Schedule of Long-term Debt Instruments (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Finance Lease Rate	15.00%
Subtotal Long-term Debt (including current portion)	$ 16,238	$ 14,757
Finance Leases	4
Less Debt Due within One Year	(245)	(18)
Long-term Debt (excluding current portion)	$ 15,993	14,739
Notes
Debt Instrument [Line Items]
Average Interest Rates	4.40%
Subtotal Long-term Debt (including current portion)	$ 16,056	14,558
Equipment Obligations
Debt Instrument [Line Items]
Average Interest Rates	6.30%
Subtotal Long-term Debt (including current portion)	$ 178	195
Finance Leases
Debt Instrument [Line Items]
Subtotal Long-term Debt (including current portion)		$ 4

Amount of short-term and long-term debt and lease obligation.

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The average effective interest rate during the reporting period.

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Present value of lessee's discounted obligation for lease payments from finance lease.

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Discount rate used by lessee to determine present value of finance lease payments.

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

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

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