Debt (Aggregate Debt Maturities) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Aggregate Debt Maturities Excluding Market Value Adjustments [Abstract]
Debt maturities - 2020	$ 1,259
Debt maturities - 2021	1,256
Debt maturities - 2022	1,802
Debt maturities - 2023	1,391
Debt maturities - 2024	1,445
Debt maturities - thereafter	19,241
Total principal	26,394
Unamortized discount and deferred issuance costs	(1,194)	$ (817)
Total debt	$ 25,200	$ 22,391

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.

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Amount of unamortized debt discount (premium) and debt issuance costs.

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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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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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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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