Leases - Other information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases
Operating cash flows from finance leases	$ 75	$ 83
Financing cash flows from finance leases	2	2
Right-of-use assets obtained in exchange for new operating lease liabilities	7	6
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 42	$ 61