Leases Leases - Lease Costs (Details) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($)
Leases [Abstract]
Variable Lease, Cost	$ 156	$ 453
Operating Lease, Cost	43	127
Finance Lease, Right-of-Use Asset, Amortization	4	12
Finance Lease, Interest Expense	10	31
Short-term Lease, Cost	2	6
Lease, Cost	$ 215	$ 629
Operating Lease, Weighted Average Remaining Lease Term	7 years 9 months 18 days	7 years 9 months 18 days
Finance Lease, Weighted Average Remaining Lease Term	29 years 3 months 18 days	29 years 3 months 18 days
Operating Lease, Weighted Average Discount Rate, Percent	5.20%	5.20%
Finance Lease, Weighted Average Discount Rate, Percent	8.60%	8.60%