Retirement Benefits - Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Pension Benefit Cost (Credit)
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 1,968	$ 2,164	$ 3,912	$ 4,329
Interest cost	8,177	8,408	16,296	16,821
Expected return on plan assets	(10,256)	(10,771)	(20,513)	(21,542)
Amortization of prior service cost	5	23	13	46
Amortization of actuarial losses (gains)	1,883	1,853	3,776	3,705
Net periodic benefit cost	1,777	1,677	3,484	3,359
Other Postretirement Benefit Credit
Defined Benefit Plan Disclosure [Line Items]
Service cost	6	7	10	14
Interest cost	151	167	302	332
Amortization of prior service cost	(14)	(5)	(29)	(10)
Amortization of actuarial losses (gains)	(86)	(84)	(172)	(168)
Net periodic benefit cost	$ 57	$ 85	$ 111	$ 168