Retirement Plans - Schedule of Net Periodic Pension Expense and Narrative (Details) - Defined Benefit Pension Plans - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Net periodic pension expense for defined benefit pension plans
Service cost	$ 4,293	$ 4,442	$ 13,084	$ 12,843
Interest cost	1,737	2,367	5,294	6,843
Expected return on assets	(7,081)	(6,667)	(21,568)	(19,260)
Amortization of prior service credit	(213)	(231)	(649)	(667)
Recognized net actuarial loss	1,406	1,204	4,282	3,476
Net periodic pension expense	142	$ 1,115	443	$ 3,235
Company contributions			13,000
Maximum
Net periodic pension expense for defined benefit pension plans
Expected contributions during 2021	$ 16,000		$ 16,000