Employee Benefit Plans - Schedule of Components of Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Pension Benefits
Components of net periodic benefit cost
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	407	593	1,221	1,778
Expected return on plan assets	(1,413)	(1,354)	(4,239)	(4,062)
Amortization of net retirement plan actuarial loss	390	353	1,170	1,058
Amortization of net retirement plan prior service (credit) cost	0	(2)	0	(7)
Net periodic benefit (income) cost	(616)	(410)	(1,848)	(1,233)
Life and Health
Components of net periodic benefit cost
Service cost	47	43	140	129
Interest cost	45	61	135	183
Expected return on plan assets	0	0	0	0
Amortization of net retirement plan actuarial loss	78	39	234	116
Amortization of net retirement plan prior service (credit) cost	(15)	(15)	(45)	(45)
Net periodic benefit (income) cost	155	128	464	383
SERP Benefits
Components of net periodic benefit cost
Service cost	58	54	173	161
Interest cost	173	228	519	685
Expected return on plan assets	0	0	0	0
Amortization of net retirement plan actuarial loss	270	200	810	600
Amortization of net retirement plan prior service (credit) cost	71	71	212	214
Net periodic benefit (income) cost	$ 572	$ 553	$ 1,714	$ 1,660