Leases - Other Information of Leases (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows used for operating leases	$ 23	$ 22
Operating cash flows used for finance leases	2	2
Financing cash flows used for finance leases	2	2
Right-of-use assets obtained in exchange for new lease obligations:
Operating leases	17	52
Finance leases	$ 17	$ 33