Lease Commitments - Assets and Liabilities of Lessee (Details) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Assets
Operating lease assets	$ 786	$ 911
Finance lease assets	63	89
Total lease assets	$ 849	$ 1,000
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Other non-current assets	Other non-current assets
Current lease liabilities
Operating	$ 194	$ 204
Finance	$ 19	$ 30
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other current liabilities	Other current liabilities
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other current liabilities	Other current liabilities
Non-current lease liabilities
Operating	$ 772	$ 897
Finance	$ 46	$ 65
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other non-current liabilities	Other non-current liabilities
Total lease liabilities	$ 1,031	$ 1,196