Leases - Supplemental Balance Sheet (Details) $ in Millions	Dec. 31, 2019 USD ($)
Assets
Operating lease assets	$ 1,686
Finance lease assets	252
Total leased assets	1,938
Current
Operating	416
Finance	35
Noncurrent
Operating	1,342
Finance	185
Total lease liabilities	$ 1,978
Weighted-average remaining lease term (years)
Operating leases	7 years 2 months 12 days
Finance leases	11 years 3 months 18 days
Weighted-average discount rate
Operating leases	6.46%
Finance leases	5.47%