Benefit Plans - Reconciliation of Funded Status (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in plan assets
Fair value of assets at beginning of year	$ 297,603
Fair value of plan assets at end of year	331,943	$ 297,603
Pension Plan
Change in benefit obligation
Benefit obligation at beginning of year	386,091	338,240
Service cost	9,730	8,659	$ 5,947
Interest cost	9,415	10,484	8,506
Actuarial (gain)/loss	(5,477)	42,164
Implicit rate subsidy	0	0
Plan participants contributions	0	0
Administrative expenses paid	(144)	(163)
Benefits paid	(15,777)	(13,293)
Benefit obligation at end of year	383,838	386,091	338,240
Change in plan assets
Fair value of assets at beginning of year	278,124	243,521
Actual return on plan assets	34,826	32,869
Employer contributions	13,147	16,609
Plan participants contributions	0	0
Administrative expenses paid	(144)	(163)
Benefits paid	(15,777)	(14,712)
Fair value of plan assets at end of year	310,176	278,124	243,521
Funded status at end of year	(73,662)	(107,967)
Other Postretirement Benefits Plan
Change in benefit obligation
Benefit obligation at beginning of year	35,794	32,546
Service cost	1,115	900	581
Interest cost	806	956	775
Actuarial (gain)/loss	(2,235)	2,421
Implicit rate subsidy	(222)	(211)
Plan participants contributions	171	254
Administrative expenses paid	0	0
Benefits paid	(1,017)	(1,072)
Benefit obligation at end of year	34,412	35,794	32,546
Change in plan assets
Fair value of assets at beginning of year	19,479	17,226
Actual return on plan assets	2,460	2,383
Employer contributions	669	675
Plan participants contributions	171	254
Administrative expenses paid	(63)	(54)
Benefits paid	(949)	(1,005)
Fair value of plan assets at end of year	21,767	19,479	$ 17,226
Funded status at end of year	$ (12,645)	$ (16,315)