Postretirement Benefits - Funding Policy/Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Postretirement benefits
Employer contributions during fiscal year	$ 25,764	$ 1,245
Net amount recognized in the Statements of Financial Position:
Funded status at end of year	(53,948)	(132,411)
Pension liabilities – due within one year	(2,724)	(2,028)
Pension liabilities – due after one year	(51,224)	(130,383)
Net amount recognized	$ (53,948)	$ (132,411)
Employee pension plan | Qualified Plan | Funded Plan
Postretirement benefits
Funding target (as a percentage of the funding target liability)	100.00%
Employer contributions during fiscal year	$ 25,000
Expected future employer contributions, 2023	$ 95,000