Postretirement Benefit Plans - Net Funded Status (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Defined Benefit Postretirement Health And Life Coverage
Change in benefit obligations:
Benefit obligations, beginning of period	$ 297,000	$ 399,000
Service cost	1,000	2,000	$ 2,000
Interest cost	13,000	8,000	9,000
Change in experience	(22,000)	(30,000)
Change in assumptions	0	(67,000)
Benefit payments	(18,000)	(15,000)
Benefit obligations, end of period	271,000	297,000	399,000
Change in fair value of plan assets:
Fair value of plan assets, beginning of period	0	0
Employer contributions	18,000	15,000
Benefit payments	(18,000)	(15,000)
Fair value of plan assets, end of period		0	0
Funded status at year end	(271,000)	(297,000)
Director's Retirement Plan
Change in benefit obligations:
Benefit obligations, beginning of period	1,299,000	1,195,000
Service cost	56,000	75,000	47,000
Interest cost	61,000	30,000	26,000
Actuarial loss	0	103,000
Change in assumptions	(12,000)	(23,000)
Benefit payments	(98,000)	(81,000)
Benefit obligations, end of period	1,306,000	1,299,000	1,195,000
Change in fair value of plan assets:
Fair value of plan assets, beginning of period	0	0
Employer contributions	98,000	81,000
Benefit payments	(98,000)	(81,000)
Fair value of plan assets, end of period	0	0	0
Funded status at year end	(1,306,000)	(1,299,000)
Scottdale Defined Benefit Pension Plan
Change in benefit obligations:
Benefit obligations, beginning of period	3,805,000	4,844,000
Service cost	58,000	69,000
Interest cost	197,000	144,000
Settlement (gain) loss	(4,000)	0
Actuarial loss	168,000	(1,096,000)
Settlement payments	(1,472,000)	0
Benefit payments	(93,000)	(156,000)
Benefit obligations, end of period	2,659,000	3,805,000	4,844,000
Change in fair value of plan assets:
Fair value of plan assets, beginning of period	4,722,000	5,302,000
Return on plan assets	348,000	(385,000)
Employer contributions	0	0
Benefit payments	(93,000)	(156,000)
Administrative expenses	(37,000)	(39,000)
Settlement payments	(1,472,000)	0
Fair value of plan assets, end of period	3,468,000	4,722,000	5,302,000
Funded status at year end	809,000	917,000
Riverview Defined Benefit Plan
Change in benefit obligations:
Benefit obligations, beginning of period	6,424,000	8,165,000
Interest cost	309,000	223,000
Actuarial loss	228,000	(1,407,000)
Benefit payments	(519,000)	(557,000)
Benefit obligations, end of period	6,442,000	6,424,000	8,165,000
Change in fair value of plan assets:
Fair value of plan assets, beginning of period	6,720,000	8,984,000
Return on plan assets	691,000	(1,709,000)
Employer contributions	3,000	2,000
Benefit payments	(519,000)	(557,000)
Fair value of plan assets, end of period	6,895,000	6,720,000	$ 8,984,000
Funded status at year end	$ 453,000	$ 296,000