Leases - Balance Sheet Classification of Lease Assets and Liabilities (Details) $ in Millions	Mar. 31, 2019 USD ($)
Leases [Abstract]
Operating lease assets	$ 343
Finance lease assets	17
Total lease assets	360
Current operating lease liabilities	78
Current finance lease liabilities	7
Noncurrent operating lease liabilities	304
Noncurrent finance lease liabilities	6
Total lease liabilities	395
Operating lease assets, net of accumulated amortization	21
Finance lease assets, net of accumulated amortization	$ 9