Leases - Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2019	Dec. 31, 2018
Assets and Liabilities, Lessee [Abstract]
Total lease assets	$ 281
Operating lease liabilities	246	$ 278
Finance lease liabilities	64
Total lease liabilities	$ 310
Minimum [Member]
Lessee, Operating Lease, Renewal Term	1 year
Maximum [Member]
Lessee, Operating Lease, Renewal Term	20 years
Other assets [Member]
Assets and Liabilities, Lessee [Abstract]
Operating lease assets	$ 225
Finance lease assets	56
Other liabilities [Member]
Assets and Liabilities, Lessee [Abstract]
Operating lease liabilities	246
Long-term Debt [Member]
Assets and Liabilities, Lessee [Abstract]
Finance lease liabilities	$ 64