Leases - Supplemental lease balance sheet information (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Leases
Non-current operating lease assets	$ 163	$ 176
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Non-current operating lease assets
Finance	$ 4	5
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property, Plant and Equipment, Net.
Total leased assets	$ 167	181
Current operating lease liabilities	$ 41	40
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Current operating lease liabilities
Operating lease liability, non current	$ 158	173
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Operating lease liability, non current
Finance lease liability, current	$ 2	2
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Other Liabilities, Current
Finance lease liability, non current	$ 1	1
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other Liabilities, Noncurrent
Total leased Liabilities	$ 202	$ 216