Leases Lessee Disclosure - Supplemental Balance Sheet Information (Details) - USD ($) $ in Millions		Jun. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Assets and Liabilities, Lessee [Abstract]
Operating lease assets, net		$ 536	$ 567	$ 0
Finance lease assets (1)	[1]	39
Total lease assets, net		575
Current portion of operating lease liabilities		131	126	0
Current portion of finance/capital lease liabilities		12		12
Long-term operating lease liabilities		465	$ 500	$ 0
Non-current portion of finance lease liabilities		21
Total lease liabilities		$ 629
Operating leases, Weighted Average Remaining Lease Term		5 years 7 months 6 days
Finance leases, Weighted Average Remaining Lease Term		3 years 3 months 18 days
Operating leases, Weighted Average Discount Rate		5.30%
Finance leases, Weighted Average Discount Rate		4.00%
Finance lease assets, Amortization		$ (35)

[1] (1) Finance lease assets are recorded net of accumulated amortization of $35 million.