Leases Leases - Lease Costs (Details) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)
Leases [Abstract]
Variable Lease, Cost	$ 153	$ 296
Operating Lease, Cost	41	82
Finance Lease, Right-of-Use Asset, Amortization	4	8
Finance Lease, Interest Expense	10	21
Short-term Lease, Cost	1	3
Lease, Cost	$ 209	$ 410
Operating Lease, Weighted Average Remaining Lease Term	8 years	8 years
Finance Lease, Weighted Average Remaining Lease Term	29 years 1 month 6 days	29 years 1 month 6 days
Operating Lease, Weighted Average Discount Rate, Percent	5.20%	5.20%
Finance Lease, Weighted Average Discount Rate, Percent	8.70%	8.70%