Leasing (Lease, Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating lease expense	$ 46	$ 45	$ 43
Variable lease expense	8	8	7
Total lease expense, net	$ 54	$ 53	$ 50