Debt - Repayments of Principal and Interest (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term Debt	$ 90,988	$ 80,717
Interest payments in 2019	2,811
Interest payments in 2020	1,816
Interest payments in 2021	1,178
Interest payments in 2022	707
Interest payments in 2023	491
Interest payments thereafter	714
Interest payments	7,717
Total repayments in 2019	33,856
Total repayments in 2020	24,969
Total repayments in 2021	16,216
Total repayments in 2022	8,137
Total repayments in 2023	5,574
Total repayments thereafter	10,651
Total repayments of principal and interest	99,403
Secured Debt [Member]
Debt Instrument [Line Items]
Repayments of principal in 2019	21,331
Repayments of principal in 2020	14,262
Repayments of principal in 2021	5,394
Repayments of principal in 2022	1,656
Repayments of principal in 2023	10
Repayments of principal thereafter	257
Long-term Debt	42,910
Unsecured Debt [Member]
Debt Instrument [Line Items]
Repayments of principal in 2019	9,714
Repayments of principal in 2020	8,891
Repayments of principal in 2021	9,644
Repayments of principal in 2022	5,774
Repayments of principal in 2023	5,073
Repayments of principal thereafter	9,680
Long-term Debt	$ 48,776

Amount of interest payments scheduled after the fifth fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the next fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the fifth fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the fourth fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the third fiscal year following the latest fiscal year.

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Amount of interest payments scheduled in the second fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled after the fifth fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the next fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the fifth fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the fourth fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the third fiscal year following the latest fiscal year.

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Amount of principal and interest payments scheduled in the second fiscal year following the latest fiscal year.

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Repayments of Principal and Interest

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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.

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Amount of interest payable on debt, including, but not limited to, trade payables.

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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.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing after the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount of long-term debt payable, sinking fund requirements, and other securities issued that are redeemable by holder at fixed or determinable prices and dates maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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