Leases - Lease Cost (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 37	$ 40
Sublease income	(6)	(3)
Short-term lease cost	0	1
Total net lease cost	$ 31	$ 38