Leases Maturity of Lease Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Leases [Abstract]
Operating Lease, Year One	$ 152	$ 154
Operating Lease, Year Two	114	120
Operating Lease, Year Three	83	93
Operating Lease, Year Four	61	67
Operating Lease, Year Five	51	47
Operating Lease, Due After Year Five	137	167
Operating Lease, Total Payments	598	648
Operating Lease, Interest	69	82
Total operating lease liabilities	529	566
Finance Lease, Year One	1	4
Finance Lease, Year Two	1	2
Finance Lease, Year Three	1	1
Finance Lease, Year Four	1	1
Finance Lease, Year Five	1	1
Finance Lease, Due After Year Five	0	1
Finance Lease, Total Payments	5	10
Finance Lease, Interest	0	1
Finance Lease, Liability	$ 5	$ 9