Financial Instruments (Credit Facilities) (Details)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Line of Credit Facility [Line Items]
Line of credit facility, maximum borrowing capacity	$ 63,000,000
Revolving credit facility, minimum interest coverage ratio	3.50
Short-term Debt	$ 0	$ 4,000,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit facility, current borrowing capacity	1,000,000,000
Line of credit facility, maximum borrowing capacity	1,500,000,000
Borrowings outstanding	0
Line Of Credit For General Corporate Purpose
Line of Credit Facility [Line Items]
Borrowings outstanding	$ 0	$ 4,000,000
Operational Efficiency
Line of Credit Facility [Line Items]
Maximum total leverage ratio	3.50
Maximum total leverage ratio, next 12 months	4.00