Leases (Supplemental Information) (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 from operating leases	$ 47	$ 47
Right-of-use assets obtained in exchange for operating liabilities:
Operating leases	48	95
Right-of-use asset balance:
Operating leases	163	159
Lease liability balance:
Current operating leases	42	34
Long-term operating leases	117	119
Total operating leases	$ 159	$ 153
Operating lease (years)	5 years 7 months 6 days	6 years 7 months 6 days
Operating lease (Percent)	5.97%	5.33%