Leases Lessee (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Lease charges	$ 50	$ 72	$ 149	$ 191
Operating lease right-of-use assets	2,642		2,642		$ 2,596
Operating Lease, Liability, Current	501		501		479
Long-term operating lease liabilities	2,166		2,166		2,140
Operating Leases, Rent Expense, Minimum Rentals	11		41
Property leases [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Cost	130	184	443	540
Variable Lease, Cost	51	93	107	219
Lease, Cost	181	$ 277	550	759
Operating lease right-of-use assets	2,642		2,642		2,596
Long-term operating lease liabilities	2,166		2,166		2,140
Operating Lease, Liability	$ 2,667		$ 2,667		$ 2,619
Operating Lease, Weighted Average Remaining Lease Term	8 years 8 months 12 days		8 years 8 months 12 days		8 years 10 months 24 days
Operating Lease, Weighted Average Discount Rate, Percent	4.01%		4.01%		4.31%
Operating Lease, Payments			$ 554	564
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability			$ (588)	$ (149)