Leasing - Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Cash Flow, Lessee [Abstract]
Operating Lease, Payments	$ 36	$ 32	$ 110	$ 93
Finance Lease, Interest Payment on Liability	0	0	1	1
Finance Lease, Principal Payments			13	9
Right-of-Use Asset Obtained in Exchange for Lease Liability [Abstract]
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	5	12	135	14
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 0	$ 1	$ 2	$ 16