Lease Commitments - Lease Assets and Liabilities (Details) $ in Millions	Sep. 30, 2019 USD ($)
Assets:
Operating lease assets	$ 1,078
Finance lease assets	97
Total leased assets	1,175
Liabilities:
Operating lease liabilities, current	463
Finance lease liabilities, current	31
Operating lease liabilities, non-current	676
Finance lease liabilities, non-current	69
Total lease liabilities	$ 1,239