Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	$ 2,626	$ 2,089	$ 5,013	$ 4,260
Employee benefit and retirement-related accounts	2,363	1,819	4,664	3,735
Investment management and investment advisory agency accounts	3,116	2,515	6,125	5,157
Other	464	370	940	754
Non-sufficient funds (NSF) fees	1,144	828	2,278	2,443
Demand deposit account (DDA) charges	774	741	1,563	1,502
Other	114	107	245	259
Credit card	636	463	1,216	1,060
HELOC	99	113	188	211
Installment	46	48	80	101
Real estate	6,011	7,775	14,449	10,422
Commercial	367	359	843	730
Debit card fee income	6,758	5,560	12,844	10,520
Bank owned life insurance income	1,149	1,179	2,314	2,427
ATM Fees	655	438	1,185	850
Gains (Losses) on Sales of Other Real Estate	4	841	(29)	645
(Gain) loss on equity securities, net	467	(977)	2,277	(1,950)
Other components of net periodic benefit income	2,038	1,988	4,076	3,976
Other	2,407	1,395	5,056	3,035
Total other income	31,238	30,964	65,327	53,450
Debt Securities, Realized Gain (Loss)	0	3,313	0	3,313
Bank Servicing [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	7,159	8,758	16,776	12,524
Within Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,300	1,100	2,600	2,300
Out of Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	5,900	7,700	14,200	10,200
PNB [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	2,626	2,089	5,013	4,260
Employee benefit and retirement-related accounts	2,363	1,819	4,664	3,735
Investment management and investment advisory agency accounts	3,116	2,515	6,125	5,157
Other	464	370	940	754
Non-sufficient funds (NSF) fees	1,144	828	2,278	2,443
Demand deposit account (DDA) charges	774	741	1,563	1,502
Other	114	107	245	259
Credit card	636	461	1,216	1,057
HELOC	99	113	188	211
Installment	46	48	80	101
Real estate	6,011	7,775	14,449	10,422
Commercial	364	307	782	678
Debit card fee income	6,758	5,560	12,844	10,520
Bank owned life insurance income	1,062	1,177	2,147	2,343
ATM Fees	655	438	1,185	850
Gains (Losses) on Sales of Other Real Estate	4	841	(29)	645
(Gain) loss on equity securities, net	495	(792)	1,329	(626)
Other components of net periodic benefit income	1,986	1,940	3,973	3,880
Other	2,409	1,359	4,934	2,986
Total other income	31,126	31,009	63,926	54,490
Debt Securities, Realized Gain (Loss)	0	3,313	0	3,313
All Other [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	0	0	0	0
Employee benefit and retirement-related accounts	0	0	0	0
Investment management and investment advisory agency accounts	0	0	0	0
Other	0	0	0	0
Non-sufficient funds (NSF) fees	0	0	0	0
Demand deposit account (DDA) charges	0	0	0	0
Other	0	0	0	0
Credit card	0	2	0	3
HELOC	0	0	0	0
Installment	0	0	0	0
Real estate	0	0	0	0
Commercial	3	52	61	52
Debit card fee income	0	0	0	0
Bank owned life insurance income	87	2	167	84
ATM Fees	0	0	0	0
Gains (Losses) on Sales of Other Real Estate	0	0	0	0
(Gain) loss on equity securities, net	(28)	(185)	948	(1,324)
Other components of net periodic benefit income	52	48	103	96
Other	(2)	36	122	49
Total other income	112	(45)	1,401	(1,040)
Debt Securities, Realized Gain (Loss)	$ 0	$ 0	$ 0	$ 0