Employee Benefit and Deferred Compensation Plans - Plan Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Change in benefit obligation
Benefit obligation at beginning of year	$ 24,945,000
Benefit obligation at end of year	28,020,000	$ 24,945,000
Change in fair value of plan assets
Fair value of plan assets at beginning of year	25,206,000
Fair value of plan assets at end of year	28,585,000	25,206,000
Pension Benefits
Change in benefit obligation
Benefit obligation at beginning of year	24,945,000	27,859,000
Service cost	0	0	$ 0
Interest cost	1,176,000	1,043,000	1,168,000
Plan participants’ contributions	0	0
Actuarial loss (gain)	3,671,000	(2,016,000)
Benefits paid	(1,772,000)	(1,941,000)
Benefit obligation at end of year	28,020,000	24,945,000	27,859,000
Change in fair value of plan assets
Fair value of plan assets at beginning of year	25,206,000	26,913,000
Actual return on plan assets	5,151,000	234,000
Contribution by employer	0	0
Benefits paid	(1,772,000)	(1,941,000)
Fair value of plan assets at end of year	28,585,000	25,206,000	26,913,000
Funded status at end of year	$ 565,000	$ 261,000
Weighted-average assumptions as of December 31
Discount rate used to determine the benefit obligation	3.59%	4.56%
Other Benefits
Change in benefit obligation
Benefit obligation at beginning of year	$ 881,000	$ 1,170,000
Service cost	7,000	8,000	9,000
Interest cost	31,000	31,000	42,000
Plan participants’ contributions	60,000	75,000
Actuarial loss (gain)	(60,000)	(239,000)
Benefits paid	(212,000)	(164,000)
Benefit obligation at end of year	707,000	881,000	$ 1,170,000
Change in fair value of plan assets
Funded status at end of year	$ (707,000)	$ (881,000)
Weighted-average assumptions as of December 31
Discount rate used to determine the benefit obligation	2.91%	4.07%