Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	$ 2,290	$ 2,151	$ 6,550	$ 6,757
Employee benefit and retirement-related accounts	1,967	1,753	5,702	5,185
Investment management and investment advisory agency accounts	2,695	2,547	7,852	7,421
Other	383	391	1,137	1,137
Non-sufficient funds (NSF) fees	1,201	1,911	3,644	5,241
Demand deposit account (DDA) charges	787	784	2,289	2,336
Other	130	169	389	501
Credit card	488	587	1,548	1,790
HELOC	108	72	319	286
Installment	43	(26)	144	120
Real estate	11,806	3,225	22,228	7,880
Commercial	602	402	1,332	1,042
Debit card fee income	5,853	5,313	16,373	14,909
Bank owned life insurance income	1,192	1,107	3,619	3,399
ATM Fees	491	482	1,341	1,382
Gains (Losses) on Sales of Other Real Estate	569	(53)	1,214	(224)
Loss (gain) on equity securities, net	1,201	3,335	(749)	5,309
Other components of net periodic benefit income	1,988	1,183	5,964	3,549
Other	2,791	2,617	5,826	5,370
Total other income	36,558	28,136	90,008	72,969
Debt Securities, Available-for-sale, Realized Gain (Loss)	(27)	186	3,286	(421)
Bank Servicing [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	13,047	4,260	25,571	11,118
Within Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,300	1,300	3,700	4,000
Out of Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	11,700	3,000	21,900	7,100
PNB [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	2,290	2,151	6,550	6,757
Employee benefit and retirement-related accounts	1,967	1,753	5,702	5,185
Investment management and investment advisory agency accounts	2,695	2,547	7,852	7,421
Other	383	391	1,137	1,137
Non-sufficient funds (NSF) fees	1,201	1,911	3,644	5,241
Demand deposit account (DDA) charges	787	784	2,289	2,336
Other	130	169	389	501
Credit card	487	586	1,544	1,785
HELOC	108	71	319	282
Installment	43	62	144	203
Real estate	11,806	3,226	22,228	7,890
Commercial	567	262	1,245	901
Debit card fee income	5,853	5,313	16,373	14,909
Bank owned life insurance income	1,109	1,021	3,452	3,116
ATM Fees	491	482	1,341	1,382
Gains (Losses) on Sales of Other Real Estate	198	(53)	843	(84)
Loss (gain) on equity securities, net	739	240	113	972
Other components of net periodic benefit income	1,940	1,147	5,820	3,440
Other	2,663	2,593	5,649	5,271
Total other income	35,430	24,842	89,920	68,224
Debt Securities, Available-for-sale, Realized Gain (Loss)	(27)	186	3,286	(421)
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	1	1	4	5
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	24	13	71	40
Other	35	45	79	97
Total other income	60	59	154	142
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	4
Installment	0	(88)	0	(83)
Real estate	0	(1)	0	(10)
Commercial	35	140	87	141
Debit card fee income	0	0	0	0
Bank owned life insurance income	83	86	167	283
ATM Fees	0	0	0	0
Gains (Losses) on Sales of Other Real Estate	371	0	371	(140)
Loss (gain) on equity securities, net	462	3,095	(862)	4,337
Other components of net periodic benefit income	24	23	73	69
Other	93	(21)	98	2
Total other income	1,068	3,235	(66)	4,603
Debt Securities, Available-for-sale, Realized Gain (Loss)	$ 0	$ 0	$ 0	$ 0