Leasing - Lease Balances (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Assets
Operating Lease, Right-of-Use Asset	$ 347	$ 391
Finance lease assets	54	38
Accumulated Amortization of Finance lease assets	(12)	(5)
Total leased assets	389	424
Liabilities
Operating lease liabilities, current	83	91
Finance lease liabilities, current	14	10
Operating lease liabilities, noncurrent	334	369
Finance lease liabilities, noncurrent	31	25
Total lease liabilities	$ 462	$ 495