Retirement Benefit Plans (Components of Net Periodic (Benefits) Cost) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]
Total recognized in other comprehensive income	$ 13,325	$ 24,139	$ 6,735
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	7,916	11,438	11,616
Interest cost	$ 23,854	$ 14,639	$ 13,476
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense
Expected return on plan assets	$ (44,710)	$ (46,615)	$ (46,654)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense
Special termination benefits			$ 16,052
Amortization of net (gain) loss/ prior service cost	$ 7,643	$ 2,830	$ 5,284
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense
Net periodic (benefit) cost	$ (5,297)	$ (17,708)	$ (226)
Net (loss) gain recognized during the year	(7,643)	(2,830)	(5,284)
Net actuarial loss (gain)	13,449	29,952	(51,365)
Total recognized in other comprehensive income	5,806	27,122	(56,649)
Total recognized in net periodic benefit cost and other comprehensive income	$ 509	$ 9,414	$ (56,875)
Discount rate for benefit obligations	4.83%	5.00%	2.77%
Discount rate for net periodic benefit cost	5.00%	2.77%	2.40%
Expected long-term return on plan assets	6.50%	5.50%	5.75%
Pension Benefits [Member] | Graded Scale, 7.25% At Age 20 [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	7.25%	7.25%	7.25%
Pension Benefits [Member] | Graded Scale, 2.25% At Age 60 [Member]
Defined Benefit Plan Disclosure [Line Items]
Rate of compensation increase	2.25%	2.25%	2.25%
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 34	$ 59	$ 93
Interest cost	$ 622	$ 375	$ 348
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense
Special termination benefits			$ 4,173
Amortization of net (gain) loss/ prior service cost	$ (843)	$ (650)	$ (729)
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense	Payroll Taxes Healthcare Costs Pension And Other Postretirement Benefit Expense
Net periodic (benefit) cost	$ (187)	$ (216)	$ 3,885
Net (loss) gain recognized during the year	843	650	729
Net actuarial loss (gain)	92	(5,906)	(1,506)
Total recognized in other comprehensive income	935	(5,256)	(777)
Total recognized in net periodic benefit cost and other comprehensive income	$ 748	$ (5,472)	$ 3,108
Discount rate for benefit obligations	4.81%	4.98%	2.32%
Discount rate for net periodic benefit cost	4.98%	2.32%	2.31%