Leases: (Other Lease Information) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities in operating cash flow	$ 243	$ 259	$ 238
Cash paid for amounts included in the measurement of lease liabilities in financing cash flows	76	26	19
Leased assets obtained in exchange for new lease liabilities	255	64	149
Leased assets obtained in exchange for new lease liabilities	$ 100	$ 89	$ 32
Weighted-average remaining lease term (years)	10 years 3 months 18 days	8 years 3 months 18 days	10 years 1 month 6 days
Weighted-average remaining lease term (years)	2 years 1 month 6 days	1 year 8 months 12 days	1 year 7 months 6 days
Weighted-average discount rate (as a percent)	3.40%	3.60%	4.30%
Weighted-average discount rate (as a percent)	4.40%	5.30%	6.70%