Revenue from Contracts with Customers Revenue from Contracts with Customers (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	$ 1,994	$ 1,995	$ 6,383	$ 5,793
Employee benefit and retirement-related accounts	1,703	1,532	5,003	4,499
Investment management and investment advisory agency accounts	2,353	2,077	6,936	6,188
Other	368	328	1,157	991
Non-sufficient funds (NSF) fees	1,926	2,100	5,608	6,100
Demand deposit account (DDA) charges	764	941	2,503	2,900
Other	171	175	498	511
Credit card	598	537	1,672	1,445
HELOC	128	123	345	348
Installment	66	54	203	331
Real estate	2,145	2,175	6,748	6,399
Commercial	309	468	1,922	1,085
Checkcard fee income	4,352	3,974	12,736	11,775
Bank owned life insurance income	2,585	1,573	4,625	3,790
ATM Fees	500	605	1,534	1,708
OREO valuation adjustments	(77)	(22)	(398)	(367)
Gain on sale of OREO, net	(81)	51	4,093	204
Other components of net periodic benefit income	1,705	1,448	5,115	4,344
Other	2,881	3,403	6,330	5,147
Total other income	24,064	23,537	74,209	63,191
Net loss on sale of investment securities (2)	0		(2,271)
Unrealized gain loss on equity securities	(326)	0	3,467	0
Bank Servicing [Member]
Disaggregation of Revenue [Line Items]
Other	3,200	3,400	10,900	9,600
Within Scope [Domain]
Disaggregation of Revenue [Line Items]
Other	1,200	1,100	4,400	3,400
Out of Scope [Domain]
Disaggregation of Revenue [Line Items]
Other	2,000	2,300	6,500	6,200
PNB [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	1,994	1,995	6,383	5,793
Employee benefit and retirement-related accounts	1,703	1,532	5,003	4,499
Investment management and investment advisory agency accounts	2,353	2,077	6,936	6,188
Other	368	328	1,157	991
Non-sufficient funds (NSF) fees	1,926	2,100	5,608	6,100
Demand deposit account (DDA) charges	764	941	2,503	2,900
Other	171	175	498	511
Credit card	592	537	1,652	1,454
HELOC	128	123	345	345
Installment	60	53	197	330
Real estate	2,145	2,144	6,748	6,368
Commercial	291	297	847	891
Checkcard fee income	4,352	3,974	12,736	11,775
Bank owned life insurance income	960	1,478	2,822	3,499
ATM Fees	500	605	1,534	1,708
OREO valuation adjustments	78	22	179	367
Gain on sale of OREO, net	36	44	1,442	192
Other components of net periodic benefit income	1,653	1,403	4,957	4,209
Other	2,685	1,986	5,637	4,080
Total other income	22,559	21,770	64,544	61,466
Net loss on sale of investment securities (2)	0		(2,271)
Unrealized gain loss on equity securities	(44)		(11)
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	6	0	20	(9)
HELOC	0	0	0	0
Installment	0	1	0	1
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	18	16	56	48
Other	39	17	59	18
Total other income	63	34	135	58
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	0	0	3
Installment	6	0	6	0
Real estate	0	31	0	31
Commercial	18	171	1,075	194
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	(1)	0	219	0
Gain on sale of OREO, net	(117)	7	2,651	12
Other components of net periodic benefit income	34	29	102	87
Other	(41)	202	(56)	150
Total other income	(99)	440	3,559	477
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	1,625	95	1,803	291
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	198	1,198	690	899
Total other income	1,541	$ 1,293	5,971	$ 1,190
Net loss on sale of investment securities (2)	0		0
Unrealized gain loss on equity securities	$ (282)		$ 3,478