Long-Term Debt - Schedule of Long-term Debt (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Debt Disclosure [Abstract]
Total borrowings at face value	$ 37,511,000,000	$ 37,401,000,000
Unamortized premium, net	765,000,000	914,000,000
Debt issuance costs	(144,000,000)	(125,000,000)
Long-term finance leases	292,000,000	347,000,000
Current finance leases	33,000,000	51,000,000
Total debt and finance leases	38,457,000,000	38,588,000,000
Less current maturities of long-term debt and financing leases	(2,558,000,000)	(51,000,000)
Long-term debt, net	$ 35,899,000,000	$ 38,537,000,000