Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	$ 2,151	$ 1,994	$ 6,757	$ 6,383
Employee benefit and retirement-related accounts	1,753	1,703	5,185	5,003
Investment management and investment advisory agency accounts	2,547	2,353	7,421	6,936
Other	391	368	1,137	1,157
Non-sufficient funds (NSF) fees	1,911	1,926	5,241	5,608
Demand deposit account (DDA) charges	784	764	2,336	2,503
Other	169	171	501	498
Credit card	587	598	1,790	1,672
HELOC	72	128	286	345
Installment	(26)	66	120	203
Real estate	3,225	2,145	7,880	6,748
Commercial	402	309	1,042	1,922
Debit card fee income	5,313	4,352	14,909	12,736
Bank owned life insurance income	1,107	2,585	3,399	4,625
ATM Fees	482	500	1,382	1,534
OREO valuation adjustments	(41)	(77)	(123)	(398)
Gain on sale of OREO, net	(53)	(81)	(224)	4,093
Other components of net periodic benefit income	1,183	1,705	3,549	5,115
Other	2,658	2,466	5,493	5,164
Total other income	28,136	24,064	72,969	74,209
Net loss on sale of investment securities (2)	186		(421)	(2,271)
Gain on equity securities, net	3,335	89	5,309	4,633
Bank Servicing [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,260	3,246	11,118	10,890
Within Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,300	1,100	4,000	4,400
Out of Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	3,000	2,100	7,100	6,500
PNB [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	2,151	1,994	6,757	6,383
Employee benefit and retirement-related accounts	1,753	1,703	5,185	5,003
Investment management and investment advisory agency accounts	2,547	2,353	7,421	6,936
Other	391	368	1,137	1,157
Non-sufficient funds (NSF) fees	1,911	1,926	5,241	5,608
Demand deposit account (DDA) charges	784	764	2,336	2,503
Other	169	171	501	498
Credit card	586	592	1,785	1,652
HELOC	71	128	282	345
Installment	62	60	203	197
Real estate	3,226	2,145	7,890	6,748
Commercial	262	291	901	847
Debit card fee income	5,313	4,352	14,909	12,736
Bank owned life insurance income	1,021	960	3,116	2,822
ATM Fees	482	500	1,382	1,534
OREO valuation adjustments	41	78	123	179
Gain on sale of OREO, net	(53)	36	(84)	1,442
Other components of net periodic benefit income	1,147	1,653	3,440	4,957
Other	2,634	2,413	5,394	5,106
Total other income	24,842	22,559	68,224	64,544
Net loss on sale of investment securities (2)	186		(421)	(2,271)
Gain on equity securities, net		228	972	520
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	6	5	20
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
OREO valuation adjustments	0	0	0	0
Gain on sale of OREO, net	0	0	0	0
Other components of net periodic benefit income	13	18	40	56
Other	45	39	97	59
Total other income	59	63	142	135
Net loss on sale of investment securities (2)	0		0	0
Gain on equity securities, net		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	1	0	4	0
Installment	(88)	6	(83)	6
Real estate	(1)	0	(10)	0
Commercial	140	18	141	1,075
Debit card fee income	0	0	0	0
Bank owned life insurance income	86	1,625	283	1,803
ATM Fees	0	0	0	0
OREO valuation adjustments	0	(1)	0	219
Gain on sale of OREO, net	0	(117)	(140)	2,651
Other components of net periodic benefit income	23	34	69	102
Other	(21)	14	2	(1)
Total other income	3,235	1,442	4,603	9,530
Net loss on sale of investment securities (2)	$ 0		0	0
Gain on equity securities, net		$ (139)	$ 4,337	$ 4,113