Leases - PAC - Schedule of Operating and Finance Lease (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Right-of-use assets:
Operating leases	$ 524	$ 517
Finance leases	448	501
Total right-of-use assets	$ 972	$ 1,018
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Lease liabilities:
Operating leases	$ 577	$ 569
Finance leases	463	514
Total lease liabilities	$ 1,040	$ 1,083
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Other current liabilities, Other long-term liabilities	Other current liabilities, Other long-term liabilities
Finance Lease, Liability, Statement of Financial Position [Extensible List]	Other current liabilities, Other long-term liabilities	Other current liabilities, Other long-term liabilities
PAC
Right-of-use assets:
Operating leases	$ 11	$ 11
Finance leases	11	17
Total right-of-use assets	$ 22	$ 28
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible Enumeration]	Other assets	Other assets
Lease liabilities:
Operating leases	$ 11	$ 11
Finance leases	12	17
Total lease liabilities	$ 23	$ 28
Operating Lease, Liability, Statement of Financial Position [Extensible List]	Other current liabilities, Other long-term liabilities	Other current liabilities, Other long-term liabilities
Finance Lease, Liability, Statement of Financial Position [Extensible List]	Other current liabilities, Other long-term liabilities	Other current liabilities, Other long-term liabilities