Components of Net Periodic Benefit Costs (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Retirement Benefits [Abstract]
Years of employment benefits are based upon			5 years
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Defined contribution plan, employer contribution amount	$ 0		$ 0
Pension Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	1,937,000	$ 1,501,000	3,874,000	$ 3,002,000
Interest cost	2,031,000	2,194,000	4,062,000	4,388,000
Expected return on plan assets	(5,737,000)	(4,727,000)	(11,474,000)	(9,454,000)
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	781,000	765,000	1,562,000	1,530,000
Net periodic (income) benefit cost	(988,000)	(267,000)	(1,976,000)	(534,000)
RIM Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	67,000	53,000	134,000	106,000
Interest cost	102,000	116,000	204,000	232,000
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	99,000	61,000	198,000	122,000
Net periodic (income) benefit cost	268,000	230,000	536,000	460,000
Post-retirement Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	99,000	84,000	198,000	168,000
Interest cost	171,000	207,000	342,000	414,000
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	0	0	0	0
Amortization of Net loss	77,000	37,000	154,000	74,000
Net periodic (income) benefit cost	347,000	328,000	694,000	656,000
Split-Dollar Life Insurance
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Service cost	120,000	88,000	226,000	176,000
Interest cost	131,000	114,000	245,000	228,000
Expected return on plan assets	0	0	0	0
Amortization of Prior service cost	14,000	14,000	28,000	28,000
Amortization of Net loss	113,000	62,000	226,000	124,000
Net periodic (income) benefit cost	378,000	$ 278,000	725,000	$ 556,000
Former Bank President | RIM Plan
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Net periodic (income) benefit cost	$ 4,000		$ 4,000