Employee Benefit Plans - Net Pension Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Components of net pension cost
Service cost - benefits earned during the year	$ 1,630	$ 1,663
Interest costs on projected benefit obligations	1,183	1,023
Expected return on plan assets	(2,231)	(1,825)
Expected administrative expenses	118	104
Amortization of prior service cost	0	0
Amortization of unrecognized net loss	0	181
Net periodic pension cost	$ 700	$ 1,146