Leases - Supplemental Balance Sheet Information Related to Leases (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Operating Leases:
Operating Lease ROU Assets	$ 668	$ 642
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	us-gaap:OtherAssets	us-gaap:OtherAssets
Finance Leases:
Property and equipment	$ 9,757	$ 9,352
Less accumulated depreciation and amortization	(4,204)	(4,030)
Property and equipment, net	5,553	5,322
Current finance lease liabilities	$ 8	$ 5
Finance Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	us-gaap:DebtCurrent	us-gaap:DebtCurrent
Long-term finance lease liabilities	$ 233	$ 74
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Long-term debt	Long-term debt
Finance Lease ROU Assets
Finance Leases:
Property and equipment	$ 314	$ 150
Less accumulated depreciation and amortization	(54)	(46)
Property and equipment, net	260	104
Finance Lease ROU Assets | Land and Improvements
Finance Leases:
Property and equipment	8	8
Finance Lease ROU Assets | Building and Building Improvements
Finance Leases:
Property and equipment	289	134
Finance Lease ROU Assets | Equipment and Fixtures
Finance Leases:
Property and equipment	$ 17	$ 8