Revenue from Contracts with Customers (Details) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	$ 2,301,000	$ 2,126,000
Employee benefit and retirement-related accounts	1,670,000	1,643,000
Investment management and investment advisory agency accounts	2,381,000	2,244,000
Other	371,000	382,000
Non-sufficient funds (NSF) fees	1,616,000	1,834,000
Demand deposit account (DDA) charges	780,000	926,000
Other	163,000	162,000
Credit card	600,000	511,000
HELOC	99,000	99,000
Installment	70,000	64,000
Real estate	1,757,000	2,246,000
Commercial	292,000	1,252,000
Debit card fee income	4,369,000	4,002,000
Bank owned life insurance income	1,006,000	1,009,000
ATM Fees	440,000	524,000
OREO valuation adjustments	(27,000)	(207,000)
Gain on sale of OREO, net	(12,000)	4,321,000
Other components of net periodic benefit income	1,183,000	1,705,000
Other	2,845,000	842,000
Total other income	22,025,000	26,903,000
Net loss on sale of investment securities (2)		(2,271,000)
Gain on equity securities, net	121,000	3,489,000
Bank Servicing [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	2,818,000	4,172,000
Within Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,200,000	1,400,000
Other	1,200,000	1,100,000
Out of Scope [Domain]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Including Assessed Tax	1,600,000	2,800,000
Other	1,600,000	(300,000)
PNB [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	2,301,000	2,126,000
Employee benefit and retirement-related accounts	1,670,000	1,643,000
Investment management and investment advisory agency accounts	2,381,000	2,244,000
Other	371,000	382,000
Non-sufficient funds (NSF) fees	1,616,000	1,834,000
Demand deposit account (DDA) charges	780,000	926,000
Other	163,000	162,000
Credit card	597,000	504,000
HELOC	95,000	99,000
Installment	74,000	64,000
Real estate	1,757,000	2,246,000
Commercial	292,000	242,000
Debit card fee income	4,369,000	4,002,000
Bank owned life insurance income	898,000	922,000
ATM Fees	440,000	524,000
OREO valuation adjustments	27,000	30,000
Gain on sale of OREO, net	(12,000)	1,585,000
Other components of net periodic benefit income	1,147,000	1,652,000
Other	1,745,000	1,032,000
Total other income	20,708,000	19,915,000
Net loss on sale of investment securities (2)		(2,271,000)
Gain on equity securities, net	51,000	27,000
GFSC [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	0	0
Employee benefit and retirement-related accounts	0	0
Investment management and investment advisory agency accounts	0	0
Other	0	0
Non-sufficient funds (NSF) fees	0	0
Demand deposit account (DDA) charges	0	0
Other	0	0
Credit card	3,000	7,000
HELOC	0	0
Installment	0	0
Real estate	0	0
Commercial	0	0
Debit card fee income	0	0
Bank owned life insurance income	0	0
ATM Fees	0	0
OREO valuation adjustments	0	0
Gain on sale of OREO, net	0	0
Other components of net periodic benefit income	13,000	19,000
Other	16,000	4,000
Total other income	32,000	30,000
Net loss on sale of investment securities (2)		0
Gain on equity securities, net	0	0
All Other [Member]
Disaggregation of Revenue [Line Items]
Personal trust and agency accounts	0	0
Employee benefit and retirement-related accounts	0	0
Investment management and investment advisory agency accounts	0	0
Other	0	0
Non-sufficient funds (NSF) fees	0	0
Demand deposit account (DDA) charges	0	0
Other	0	0
Credit card	0	0
HELOC	4,000	0
Installment	(4,000)	0
Real estate	0	0
Commercial	0	1,010,000
Debit card fee income	0	0
Bank owned life insurance income	108,000	87,000
ATM Fees	0	0
OREO valuation adjustments	0	177,000
Gain on sale of OREO, net	0	2,736,000
Other components of net periodic benefit income	23,000	34,000
Other	1,084,000	(194,000)
Total other income	1,285,000	6,958,000
Net loss on sale of investment securities (2)		0
Gain on equity securities, net	$ 70,000	$ 3,462,000