Leases Leases - Maturity Table (Details) - USD ($) $ in Millions		Dec. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Operating Leases, Future Minimum Payments Due, Next Twelve Months	[1]		$ 147
Lessee, Operating Lease, Liability, Payments, Due Next Twelve Months		$ 147
Finance Lease, Liability, Payments, Due Next Twelve Months		71
Lease, Liability, Payments, Due Next Twelve Months		218	216	[1]
Lessee, Operating Lease, Liability, Payments, Due Year Two		126
Finance Lease, Liability, Payments, Due Year Two		77
Lease, Liability, Payments, Due Year Two		203	196	[1]
Lessee, Operating Lease, Liability, Payments, Due Year Three		102
Finance Lease, Liability, Payments, Due Year Three		70
Lease, Liability, Payments, Due Year Three		172	183	[1]
Lessee, Operating Lease, Liability, Payments, Due Year Four		73
Finance Lease, Liability, Payments, Due Year Four		59
Lease, Liability, Payments, Due Year Four		132	154	[1]
Lessee, Operating Lease, Liability, Payments, Due Year Five		50
Finance Lease, Liability, Payments, Due Year Five		59
Lease, Liability, Payments, Due Year Five		109	117	[1]
Lessee, Operating Lease, Liability, Payments, Due after Year Five		202
Finance Lease, Liability, Payments, Due after Year Five		725
Lease, Liability, Payments, Due after Year Five		927	931	[1]
Lessee, Operating Lease, Liability, Payments, Due		700
Finance Lease, Liability, Payment, Due		1,061
Lease, Liability, Payments, Due		1,761	1,797	[1]
Lessee, Operating Lease, Liability, Undiscounted Excess Amount		(123)
Finance Lease, Liability, Undiscounted Excess Amount		(542)
Lease, Liability, Undiscounted Excess Amount		(665)
Operating Lease, Liability		577
Finance Lease, Liability		519
Total Lease Liabilities		$ 1,096
Capital Leases, Future Minimum Payments Due, Next Twelve Months	[1]		69
Operating Leases, Future Minimum Payments, Due in Two Years	[1]		128
Capital Leases, Future Minimum Payments Due in Two Years	[1]		68
Operating Leases, Future Minimum Payments, Due in Three Years	[1]		110
Capital Leases, Future Minimum Payments Due in Three Years	[1]		73
Operating Leases, Future Minimum Payments, Due in Four Years	[1]		87
Capital Leases, Future Minimum Payments Due in Four Years	[1]		67
Operating Leases, Future Minimum Payments, Due in Five Years	[1]		61
Capital Leases, Future Minimum Payments Due in Five Years	[1]		56
Operating Leases, Future Minimum Payments, Due Thereafter	[1]		159
Capital Leases, Future Minimum Payments Due Thereafter	[1]		772
Operating Leases, Future Minimum Payments Due	[1]		692
Capital Leases, Future Minimum Payments Due	[1]		$ 1,105

[1] Amounts included for comparability and accounted for in accordance with ASC Topic 840, "Leases".