Leases (Supplemental Balance Sheet Information) (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Operating Leases:
Operating lease right-of-use assets, net	[1]	$ 504
Other current liabilities		62
Operating lease liabilities	[2]	450
Total operating lease liabilities		512
Finance Leases:
Property and equipment, at cost		28,332	$ 26,827
Accumulated depreciation		(12,995)	(11,932)
Property and equipment, net		15,337	$ 14,895
Current portion of long-term debt		9
Long-term debt		271
Total finance lease liabilities		280
Leaseholds and Leasehold Improvements [Member]
Finance Leases:
Property and equipment, at cost		294
Accumulated depreciation		(52)
Property and equipment, net		$ 242

[1] Included in other assets.

[2] Included in other liabilities.