Leases Supplemental Lease Disclosures (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Leases [Abstract]
Operating Lease, Payments	$ 32
Finance Lease, Interest Payment on Liability	1
Finance Lease, Principal Payments	2
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	19
Sale and Leaseback Transaction, Gain (Loss), Net	$ 36
Operating Lease, Weighted Average Remaining Lease Term	6 years 8 months
Finance Lease, Weighted Average Remaining Lease Term	7 years 11 months
Operating Lease, Weighted Average Discount Rate, Percent	13.10%
Finance Lease, Weighted Average Discount Rate, Percent	5.60%