Leases - Supplemental cash flow information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Leases [Abstract]
Operating cash flows for operating leases	$ 27	$ 12
Financing cash flows for finance leases	1	1
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	11	11
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 1	$ 2