Leases Supplemental Cash Flow Information (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Supplemental Cash Flow Information [Abstract]
Operating Lease, Payments	$ 96
Finance Lease, Interest Payment on Liability	7
Finance Lease, Principal Payments	22
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	119
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 1