Leases (Components of Lease Expense) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2017
Operating lease costs:
Operating lease cost	$ 49
Short-term lease cost	4
Total operating lease costs	53
Finance lease cost:
Amortization of right-of-use assets	1
Total finance lease costs	$ 1
Operating Leases, Rent Expense, Net		$ 50