Leases - Lease Assets and Liabilities (Details) $ in Millions	Mar. 31, 2019 USD ($)
Assets:
Operating lease assets	$ 684
Finance lease assets	23
Total leased assets	707
Liabilities:
Current lease liabilities	240
Lease liabilities	465
Total lease liabilities	705
Current lease liabilities
Liabilities:
Current lease liabilities	229
Finance, liability, current	11
Deferred credits and other liabilities - Lease liabilities
Liabilities:
Lease liabilities	453
Finance, liability, noncurrent	$ 12