Retirement Benefit Plans (Changes in Benefit Obligations and Plan Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	$ 646,832	$ 660,309
Service cost	11,438	11,616	$ 12,898
Interest cost	$ 14,639	$ 13,476	$ 16,207
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
Net actuarial gain	$ (152,009)	$ (16,000)
Special termination benefits		16,052
Benefits paid	(25,154)	(38,621)
Benefit obligation, end of year	495,746	646,832	$ 660,309
Fair value of plan assets at beginning of year	859,883	815,304
Actual return on plan assets	(133,843)	83,939
Employer contributions	1,150	1,181
Benefit payments	(25,154)	(38,621)
Expenses	(1,501)	(1,920)
Fair value of plan assets, end of year	700,535	859,883	815,304
Funded status at end of year - net asset (liability)	204,789	213,051
Unrecognized loss (gain) at beginning of year	108,121	164,770
Net actuarial loss (gain)	27,122	(56,649)
Unrecognized loss (gain) at end of year	135,243	108,121	164,770
Accumulated benefit obligation	472,843	607,408
Other Post-Retirement Benefits [Member]
Defined Benefit Plan Disclosure [Line Items]
Benefit obligation at beginning of year	20,282	18,330
Service cost	59	93	105
Interest cost	$ 375	$ 348	$ 484
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
Plan participants' contributions	$ 794	$ 778
Net actuarial gain	(5,906)	(1,506)
Special termination benefits		4,173
Benefits paid	(1,808)	(1,934)
Benefit obligation, end of year	13,796	20,282	$ 18,330
Employer contributions	1,015	1,156
Plan participants' contributions	793	778
Benefit payments	(1,808)	(1,934)
Funded status at end of year - net asset (liability)	(13,796)	(20,282)
Unrecognized loss (gain) at beginning of year	(3,581)	(2,804)
Net actuarial loss (gain)	(5,256)	(777)
Unrecognized loss (gain) at end of year	$ (8,837)	$ (3,581)	$ (2,804)