Leasing - Lease Balances (Details) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Assets
Operating Lease, Right-of-Use Asset	$ 347	$ 391
Finance lease assets	55	38
Accumulated amortization of finance lease assets	(15)	(5)
Total leased assets	387	424
Liabilities
Operating lease liabilities, current	82	91
Finance lease liabilities, current	15	10
Operating lease liabilities, noncurrent	336	369
Finance lease liabilities, noncurrent	27	25
Total lease liabilities	$ 460	$ 495