Leasing - Lease Balances (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Assets
Operating lease assets	$ 423	$ 344
Finance lease assets	64	55
Accumulated amortization of finance lease assets	(31)	(18)
Total leased assets	456	381
Liabilities
Operating lease liabilities, current	102	85
Finance lease liabilities, current	17	15
Operating lease liabilities, noncurrent	406	325
Finance lease liabilities, noncurrent	17	23
Total lease liabilities	$ 542	$ 448