Leases (Schedule of Total Lease Cost) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost		$ 10	$ 40
Short-term lease cost	[1]	45	84
Financing lease cost:
Amortization of right-of-use assets		8	8
Interest on lease liabilities		11	10
Variable lease cost			2
Lease income		(8)	(5)
Net lease cost		$ 66	$ 139

[1] Short-term lease cost excludes leases with terms of one month or less.