Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	$ 2,089	$ 2,305	$ 4,260	$ 4,606
Employee benefit and retirement-related accounts	1,819	1,762	3,735	3,432
Investment management and investment advisory agency accounts	2,515	2,493	5,157	4,874
Other	370	375	754	746
Non-sufficient funds (NSF) fees	828	1,714	2,443	3,330
Demand deposit account (DDA) charges	741	772	1,502	1,552
Other	107	169	259	332
Credit card	463	603	1,060	1,203
HELOC	113	115	211	214
Installment	48	76	101	146
Real estate	7,775	2,898	10,422	4,655
Commercial	359	348	730	640
Debit card fee income	5,560	5,227	10,520	9,596
Bank owned life insurance income	1,179	1,286	2,427	2,292
ATM Fees	438	460	850	900
Gains (Losses) on Sales of Other Real Estate	841	(159)	645	(171)
Loss (gain) on equity securities, net	(977)	232	(1,950)	1,974
Other components of net periodic benefit income	1,988	1,183	3,976	2,366
Other	1,395	1,556	3,035	2,753
Total other income	30,964	22,808	53,450	44,833
Debt Securities, Available-for-sale, Realized Gain (Loss)	3,313	(607)	3,313	(607)
Bank Servicing [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	8,758	4,040	12,524	6,858
Within Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,100	1,200	2,300	2,400
Out of Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	7,700	2,800	10,200	4,500
PNB [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	2,089	2,305	4,260	4,606
Employee benefit and retirement-related accounts	1,819	1,762	3,735	3,432
Investment management and investment advisory agency accounts	2,515	2,493	5,157	4,874
Other	370	375	754	746
Non-sufficient funds (NSF) fees	828	1,714	2,443	3,330
Demand deposit account (DDA) charges	741	772	1,502	1,552
Other	107	169	259	332
Credit card	461	602	1,057	1,199
HELOC	113	116	211	211
Installment	48	67	101	141
Real estate	7,775	2,907	10,422	4,664
Commercial	307	347	678	639
Debit card fee income	5,560	5,227	10,520	9,596
Bank owned life insurance income	1,177	1,197	2,343	2,095
ATM Fees	438	460	850	900
Gains (Losses) on Sales of Other Real Estate	841	(19)	645	(31)
Loss (gain) on equity securities, net	(792)	143	(626)	732
Other components of net periodic benefit income	1,940	1,146	3,880	2,293
Other	1,359	1,498	2,986	2,678
Total other income	31,009	22,674	54,490	43,382
Debt Securities, Available-for-sale, Realized Gain (Loss)	3,313	(607)	3,313	(607)
GFSC [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	2	1	3	4
HELOC	0	0	0	0
Installment	0	0	0	0
Real estate	0	0	0	0
Commercial	0	0	0	0
Debit card fee income	0	0	0	0
Bank owned life insurance income	0	0	0	0
ATM Fees	0	0	0	0
Gains (Losses) on Sales of Other Real Estate	0	0	0	0
Loss (gain) on equity securities, net	0	0	0	0
Other components of net periodic benefit income	23	14	47	27
Other	37	36	44	52
Total other income	62	51	94	83
Debt Securities, Available-for-sale, Realized Gain (Loss)	0	0	0	0
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	0	0	0
HELOC	0	(1)	0	3
Installment	0	9	0	5
Real estate	0	(9)	0	(9)
Commercial	52	1	52	1
Debit card fee income	0	0	0	0
Bank owned life insurance income	2	89	84	197
ATM Fees	0	0	0	0
Gains (Losses) on Sales of Other Real Estate	0	(140)	0	(140)
Loss (gain) on equity securities, net	(185)	89	(1,324)	1,242
Other components of net periodic benefit income	25	23	49	46
Other	(1)	22	5	23
Total other income	(107)	83	(1,134)	1,368
Debt Securities, Available-for-sale, Realized Gain (Loss)	$ 0	$ 0	$ 0	$ 0