Pension and Other Post Retirement Benefit Plans - Schedule of Changes in Benefit Obligation, and Plan Assets, Funded Status of the Plan, Assets and Liabilities Recognized in the Balance Sheets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Change in Benefit Obligation:
Benefit obligation at beginning of year	$ 76,770	$ 73,193
Service cost	16	39	$ 8
Interest cost	2,343	2,975	2,816
Actuarial (gain) loss	6,957	4,007
Benefits paid	(5,300)	(5,145)
Net transfer in from MBT acquisition	0	1,701
Benefit obligation at end of year	80,786	76,770	73,193
Change in Plan Assets:
Fair value of plan assets at beginning of year	85,121	76,736
Actual return on plan assets	7,925	12,972
Employer contributions	766	558
Benefits paid	(5,300)	(5,145)
End of year	88,512	85,121	$ 76,736
Funded status at end of year	7,726	8,351
Assets and Liabilities Recognized in the Balance Sheets:
Deferred tax asset	3,970	3,278
Assets	12,681	13,291
Liabilities	$ 4,955	$ 4,940