Leases Supplemental cash flow information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating cash flows from operating leases	$ 37	$ 36
Operating cash flows from finance leases	15	19
Financing cash flows from finance leases	29	23
ROU assets obtained in exchange for finance lease liabilities	78	0	$ 0
ROU assets obtained in exchange for operating lease liabilities	$ 58	$ 11