Retirement Benefits - Components of Net Periodic Benefit Cost (Credit) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Pension Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 2,229	$ 3,300
Interest cost	8,709	5,159
Expected return on plan assets	(10,189)	(17,314)
Amortization of prior service cost	28	55
Amortization of actuarial losses (gains)	2,945	1,155
Net periodic benefit cost (credit)	3,722	(7,645)
Other Postretirement Benefit Plans, Defined Benefit
Defined Benefit Plan Disclosure [Line Items]
Service cost	14	25
Interest cost	189	109
Amortization of prior service cost	(235)	(416)
Amortization of actuarial losses (gains)	(161)	(77)
Net periodic benefit cost (credit)	$ (193)	$ (359)