Retirement Benefits - Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Pension Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,937	$ 3,177	$ 9,507	$ 10,754
Interest cost	5,131	4,579	15,430	13,288
Expected return on plan assets	(17,220)	(19,892)	(51,849)	(59,590)
Amortization of prior service cost	62	67	170	183
Amortization of actuarial losses (gains)	1,370	3,464	3,682	9,518
Net periodic benefit credit	(7,720)	(8,605)	(23,060)	(25,847)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	5	25	56	81
Interest cost	96	82	314	272
Amortization of prior service cost	(415)	(460)	(1,247)	(1,373)
Amortization of actuarial losses (gains)	(75)	(137)	(229)	(232)
Net periodic benefit credit	$ (389)	$ (490)	$ (1,106)	$ (1,252)