Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	$ 2,305	$ 2,263	$ 4,606	$ 4,389
Employee benefit and retirement-related accounts	1,762	1,657	3,432	3,300
Investment management and investment advisory agency accounts	2,493	2,339	4,874	4,583
Other	375	407	746	789
Non-sufficient funds (NSF) fees	1,714	1,848	3,330	3,682
Demand deposit account (DDA) charges	772	813	1,552	1,739
Other	169	165	332	327
Credit card	603	563	1,203	1,074
HELOC	115	118	214	217
Installment	76	73	146	137
Real estate	2,898	2,357	4,655	4,603
Commercial	348	361	640	1,613
Debit card fee income	5,227	4,382	9,596	8,384
Bank owned life insurance income	1,286	1,031	2,292	2,040
ATM Fees	460	510	900	1,034
OREO valuation adjustments	(55)	(114)	(82)	(321)
Gain on sale of OREO, net	(159)	(147)	(171)	4,174
Other components of net periodic benefit income	1,183	1,705	2,366	3,410
Other	1,611	1,563	2,835	2,698
Total other income	22,808	23,242	44,833	50,145
Net loss on sale of investment securities (2)	(607)	0	(607)	(2,271)
Gain on equity securities, net	232	1,348	1,974	4,544
Bank Servicing [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	4,040	3,472	6,858	7,644
Within Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,600	1,200	2,800	3,200
Out of Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,400	2,300	4,100	4,400
PNB [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	2,305	2,263	4,606	4,389
Employee benefit and retirement-related accounts	1,762	1,657	3,432	3,300
Investment management and investment advisory agency accounts	2,493	2,339	4,874	4,583
Other	375	407	746	789
Non-sufficient funds (NSF) fees	1,714	1,848	3,330	3,682
Demand deposit account (DDA) charges	772	813	1,552	1,739
Other	169	165	332	327
Credit card	602	556	1,199	1,060
HELOC	116	118	211	217
Installment	67	73	141	137
Real estate	2,907	2,357	4,664	4,603
Commercial	347	314	639	556
Debit card fee income	5,227	4,382	9,596	8,384
Bank owned life insurance income	1,197	940	2,095	1,862
ATM Fees	460	510	900	1,034
OREO valuation adjustments	55	71	82	101
Gain on sale of OREO, net	(19)	(179)	(31)	1,406
Other components of net periodic benefit income	1,146	1,652	2,293	3,304
Other	1,553	1,546	2,760	2,693
Total other income	22,674	22,070	43,382	41,985
Net loss on sale of investment securities (2)	(607)	0	(607)	(2,271)
Gain on equity securities, net		380	732	292
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	7	4	14
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	14	19	27	38
Other	36	16	52	20
Total other income	51	42	83	72
Net loss on sale of investment securities (2)	0	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	3	0
Installment	9	0	5	0
Real estate	(9)	0	(9)	0
Commercial	1	47	1	1,057
Debit card fee income	0	0	0	0
Bank owned life insurance income	89	91	197	178
ATM Fees	0	0	0	0
OREO valuation adjustments	0	43	0	220
Gain on sale of OREO, net	(140)	32	(140)	2,768
Other components of net periodic benefit income	23	34	46	68
Other	22	1	23	(15)
Total other income	83	1,130	1,368	8,088
Net loss on sale of investment securities (2)	$ 0	0	0	0
Gain on equity securities, net		$ 968	$ 1,242	$ 4,252