Leasing Leasing (Lease, Cost) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Leases [Abstract]
Operating lease expense	$ 45	$ 43	$ 42
Variable lease expense	8	7	7
Total lease expense, net	$ 53	$ 50	$ 49