Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	$ 2,263	$ 2,012	$ 4,389	$ 3,798
Employee benefit and retirement-related accounts	1,657	1,517	3,300	2,967
Investment management and investment advisory agency accounts	2,339	2,143	4,583	4,111
Other	407	353	789	663
Non-sufficient funds (NSF) fees	1,848	2,015	3,682	4,000
Demand deposit account (DDA) charges	813	974	1,739	1,959
Other	165	167	327	336
Credit card	563	488	1,074	908
HELOC	118	134	217	225
Installment	73	119	137	277
Real estate	2,357	2,412	4,603	4,224
Commercial	361	294	1,613	617
Checkcard fee income	4,382	4,040	8,384	7,801
Bank owned life insurance income	1,031	1,114	2,040	2,217
ATM Fees	510	561	1,034	1,103
OREO valuation adjustments	(114)	(272)	(321)	(345)
Gain on sale of OREO, net	(147)	53	4,174	153
Other components of net periodic benefit income	1,705	1,448	3,410	2,896
Other	2,607	1,127	3,449	1,744
Total other income	23,242	20,699	50,145	39,654
Net loss on sale of investment securities (2)	0		(2,271)
Unrealized gain loss on equity securities	304	0	3,793	0
Bank Servicing [Member]
Disaggregation of Revenue [Line Items]
Other	3,500	3,500	7,600	6,300
Within Scope [Domain]
Disaggregation of Revenue [Line Items]
Other	2,400	2,500	5,500	4,400
Out of Scope [Domain]
Disaggregation of Revenue [Line Items]
Other	1,100	1,000	2,100	1,900
PNB [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	2,263	2,012	4,389	3,798
Employee benefit and retirement-related accounts	1,657	1,517	3,300	2,967
Investment management and investment advisory agency accounts	2,339	2,143	4,583	4,111
Other	407	353	789	663
Non-sufficient funds (NSF) fees	1,848	2,015	3,682	4,000
Demand deposit account (DDA) charges	813	974	1,739	1,959
Other	165	167	327	336
Credit card	556	497	1,060	917
HELOC	118	131	217	222
Installment	73	119	137	277
Real estate	2,357	2,412	4,603	4,224
Commercial	314	271	556	594
Checkcard fee income	4,382	4,040	8,384	7,801
Bank owned life insurance income	940	1,014	1,862	2,021
ATM Fees	510	561	1,034	1,103
OREO valuation adjustments	71	272	101	345
Gain on sale of OREO, net	(179)	48	1,406	148
Other components of net periodic benefit income	1,652	1,403	3,304	2,806
Other	1,920	1,177	2,952	2,094
Total other income	22,070	20,582	41,985	39,696
Net loss on sale of investment securities (2)	0		(2,271)
Unrealized gain loss on equity securities	6		33
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	7	(9)	14	(9)
HELOC	0	0	0	0
Installment	0	0	0	0
Real estate	0	0	0	0
Commercial	0	0	0	0
Checkcard 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	19	16	38	32
Other	16	1	20	1
Total other income	42	8	72	24
Net loss on sale of investment securities (2)	0		0
Unrealized gain loss on equity securities	0		0
SEPH [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	3	0	3
Installment	0	0	0	0
Real estate	0	0	0	0
Commercial	47	23	1,057	23
Checkcard fee income	0	0	0	0
Bank owned life insurance income	0	0	0	0
ATM Fees	0	0	0	0
OREO valuation adjustments	43	0	220	0
Gain on sale of OREO, net	32	5	2,768	5
Other components of net periodic benefit income	34	29	68	58
Other	1	(52)	(15)	(52)
Total other income	71	8	3,658	37
Net loss on sale of investment securities (2)	0		0
Unrealized gain loss on equity securities	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	0	0	0
Installment	0	0	0	0
Real estate	0	0	0	0
Commercial	0	0	0	0
Checkcard fee income	0	0	0	0
Bank owned life insurance income	91	100	178	196
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	0	0	0	0
Other	670	1	492	(299)
Total other income	1,059	$ 101	4,430	$ (103)
Net loss on sale of investment securities (2)	0		0
Unrealized gain loss on equity securities	$ 298		$ 3,760