Lease Obligations - Lessee - Other Information (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Lease Obligationgs Other Information [Line Items]
Finance Lease Weighted Average Discount Rate, Percent	5.86%
Operating Lease Weighted Average Discount Rate, Percent	3.28%
Operating Lease Weighted Average Remaining Lease Term	9 years 25 days
Finance Lease Weighted Average Remaining Lease Term	4 years 5 months 19 days
Gains and losses on sale and leaseback transations, net	$ 0
Lease liability
Lease Obligationgs Other Information [Line Items]
Operating Cash Flows from Operating Leases	47
Operating Cash Flows from Finance Leases	1
Financing Cash Flows from Finance Leases	$ 2