Retirement Plans - Schedule of Benefit Obligation and Plan Assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in fair value of plan assets:
Fair value of plan assets, beginning of period	$ 32,853
Fair value of plan assets, end of period	170,215	$ 32,853
Pension Plans
Change in benefit obligation:
Benefit obligation, beginning of period	28,330	31,389
Benefit obligation acquired in Merger	136,587	0
Service cost	0	0	$ 0
Interest cost on benefit obligation	3,013	983	1,138
Actuarial (gain) loss	3,831	(630)	765
Benefits paid	(5,785)	(3,412)
Benefit obligation, end of period	165,976	28,330	31,389
Change in fair value of plan assets:
Fair value of plan assets, beginning of period	32,844	36,863
Fair value of plan assets acquired in Merger	141,746	0
Actual gain (loss) on plan assets	333	(607)
Benefits paid	(5,439)	(3,412)
Employer contributions	0	0	0
Fair value of plan assets, end of period	169,484	32,844	36,863
Funded status of plan, end of period	3,508	4,514
Accumulated benefit obligation	165,976	28,330
Amounts recognized in the Consolidated Statements of Financial Condition:
Prepaid (accrued) benefit cost, end of period	3,508	4,514
Prior service cost included in accumulated other comprehensive income (loss)	0	0
Postretirement Plans
Change in benefit obligation:
Benefit obligation, beginning of period	3,320	3,717
Benefit obligation acquired in Merger	2,271	0
Service cost	1	0	0
Interest cost on benefit obligation	149	110	133
Actuarial (gain) loss	(19)	(115)	(248)
Benefits paid	(446)	(392)
Benefit obligation, end of period	5,276	3,320	3,717
Change in fair value of plan assets:
Fair value of plan assets, beginning of period	0	0
Fair value of plan assets acquired in Merger	0	0
Actual gain (loss) on plan assets	0	0
Benefits paid	(377)	(392)
Employer contributions	377	392	332
Fair value of plan assets, end of period	0	0	$ 0
Funded status of plan, end of period	(5,276)	(3,320)
Amounts recognized in the Consolidated Statements of Financial Condition:
Prepaid (accrued) benefit cost, end of period	(5,276)	(3,320)
Prior service cost included in accumulated other comprehensive income (loss)	$ (101)	$ (147)