Leases, Additional Information (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
ROU assets, net reflected in the following balance sheet line items:
Operating lease ROU assets, net, balance sheet line item	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Operating leases - deferred charges and other assets, net	$ 1,234	$ 1,329
Current lease liabilities reflected in the following balance sheet line items:
Current operating lease liabilities, balance sheet line item	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Operating leases - accrued expenses	$ 301	$ 331
Noncurrent lease liabilities reflected in the following balance sheet line items:
Noncurrent operating lease liabilities, balance sheet line item	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Operating leases - other long-term liabilities	$ 904	$ 959
Operating leases - total lease liabilities	$ 1,205	$ 1,290
ROU assets, net reflected in the following balance sheet line items:
Finance lease ROU assets, net, balance sheet line item	us-gaap:PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization	us-gaap:PropertyPlantAndEquipmentAndFinanceLeaseRightOfUseAssetAfterAccumulatedDepreciationAndAmortization
Finance leases - property, plant, and equipment, net	$ 2,208	$ 790
Current lease liabilities reflected in the following balance sheet line items:
Current finance lease liabilities, balance sheet line item	us-gaap:DebtCurrent	us-gaap:DebtCurrent
Finance leases - current portion of debt and finance lease obligations	$ 80	$ 41
Noncurrent lease liabilities reflected in the following balance sheet line items:
Noncurrent finance lease liabilities, balance sheet line item	us-gaap:LongTermDebtAndCapitalLeaseObligations	us-gaap:LongTermDebtAndCapitalLeaseObligations
Finance leases - debt and finance lease obligations, less current portion	$ 2,166	$ 750
Finance leases - total lease liabilities	$ 2,246	$ 791
Operating Leases
Weighted-average remaining lease term	7 years 7 months 6 days	7 years 8 months 12 days
Weighted-average discount rate	4.70%	4.90%
Finance Leases
Weighted-average remaining lease term	22 years 1 month 6 days	19 years 8 months 12 days
Weighted-average discount rate	4.30%	5.20%