Leases (Other Information) (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows from operating leases	$ 108	$ 104
Operating cash flows from finance leases	2	6
Financing cash flows from finance leases	42	26
Leased assets obtained in exchange for new operating lease liabilities (1)	184	92
Leased assets obtained in exchange for new finance lease liabilities	$ 39	$ 39