Leases - Supplemental Balance Sheet Information (Details) $ in Millions	Sep. 30, 2019 USD ($)
Assets:
ROU operating lease assets	$ 1,482
ROU finance lease assets	1,291
Total	2,773
Current
Operating lease	489
Finance lease	488
Total	977
Non-current
Operating lease	1,139
Finance lease	688
Total	$ 1,827
Weighted Average remaining lease term:
Operating leases	4 years 9 months 18 days
Finance leases	2 years 10 months 24 days
Weighted average remaining discount rate:
Operating leases	3.30%
Finance leases	5.40%