Leases Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019
Operating Lease, Payments	$ 107	$ 203
Finance Lease, Interest Payment on Liability	7	14
Finance Lease, Principal Payments	21	43
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	5	124
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 0	$ 1