Leases (Lease Costs) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Finance Lease, Right-of-Use Asset, Amortization	$ 28	$ 7
Finance Lease, Interest Expense	17	4
Operating Lease, Cost	151	200
Short-term Lease, Cost	23	33
Variable Lease, Cost	27	73
Total lease cost	$ 246	$ 317