Leases - Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Assets and Liabilities, Lessee [Abstract]
Total lease assets	$ 271
Operating lease liabilities	248	$ 278
Finance lease liabilities	55
Total lease liabilities	$ 303
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	46
Other liabilities [Member]
Assets and Liabilities, Lessee [Abstract]
Operating lease liabilities	248
Long-term Debt [Member]
Assets and Liabilities, Lessee [Abstract]
Finance lease liabilities	$ 55