Leases Lessee (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Lease charges	$ 56	$ 57
Operating lease right-of-use assets	2,686		$ 2,596
Operating Lease, Liability, Current	512		479
Long-term operating lease liabilities	2,198		2,140
Property leases [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	185	177
Variable Lease, Cost	36	51
Lease, Cost	221	228
Operating lease right-of-use assets	2,686		2,596
Long-term operating lease liabilities	2,198		2,140
Operating Lease, Liability	$ 2,710		$ 2,619
Operating Lease, Weighted Average Remaining Lease Term	9 years		8 years 10 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent	4.23%		4.31%
Operating Lease, Payments	$ 170	189
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ (296)	$ (113)