Loans, Credit Risk Profile Based on Rating Category and Payment Activity and on Performing and Nonperforming Status, Segregated by Class (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2018	Dec. 31, 2017
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		$ 3,177,888	$ 3,122,940
Consumer mortgage loans secured by real estate properties for which formal foreclosure proceedings are in process		4,400	3,700
Commercial [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		1,613,735	1,619,235
Commercial [Member] | Pass [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		$ 1,400,940	1,430,207
Commercial [Member] | Pass [Member] | Minimum [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Review period for loans		12 months
Commercial [Member] | Pass [Member] | Maximum [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Review period for loans		18 months
Commercial [Member] | Watch [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		$ 107,822	97,513
Commercial [Member] | OAEM [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		26,435	26,948
Commercial [Member] | Substandard [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		78,347	63,998
Commercial [Member] | Doubtful [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		191	569
Commercial [Member] | Construction [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		81,472	76,479
Commercial [Member] | Construction [Member] | Pass [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		74,592	67,846
Commercial [Member] | Construction [Member] | Watch [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		3,133	3,323
Commercial [Member] | Construction [Member] | OAEM [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		1,626	1,304
Commercial [Member] | Construction [Member] | Substandard [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		2,121	3,828
Commercial [Member] | Construction [Member] | Doubtful [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		0	178
Commercial [Member] | Real Estate [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		1,183,632	1,188,680
Commercial [Member] | Real Estate [Member] | Pass [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		1,029,800	1,053,701
Commercial [Member] | Real Estate [Member] | Watch [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		74,669	65,182
Commercial [Member] | Real Estate [Member] | OAEM [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		17,906	22,401
Commercial [Member] | Real Estate [Member] | Substandard [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		61,146	47,223
Commercial [Member] | Real Estate [Member] | Doubtful [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		111	173
Commercial [Member] | Equipment Leases [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		1,986	3,042
Commercial [Member] | Equipment Leases [Member] | Pass [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		1,986	3,005
Commercial [Member] | Equipment Leases [Member] | Watch [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		0	0
Commercial [Member] | Equipment Leases [Member] | OAEM [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		0	37
Commercial [Member] | Equipment Leases [Member] | Substandard [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		0	0
Commercial [Member] | Equipment Leases [Member] | Doubtful [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		0	0
Commercial [Member] | Other [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		346,645	351,034
Commercial [Member] | Other [Member] | Pass [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		294,562	305,655
Commercial [Member] | Other [Member] | Watch [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		30,020	29,008
Commercial [Member] | Other [Member] | OAEM [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		6,903	3,206
Commercial [Member] | Other [Member] | Substandard [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		15,080	12,947
Commercial [Member] | Other [Member] | Doubtful [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		80	218
Residential [Member] | Construction [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		61,782	67,358
Residential [Member] | Construction [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		61,749	66,817
Residential [Member] | Construction [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile	[1]	33	541
Residential [Member] | Real Estate [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		722,022	709,570
Residential [Member] | Real Estate [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		711,208	695,034
Residential [Member] | Real Estate [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile	[1]	10,814	14,536
Residential [Member] | Home Equity [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		103,805	99,356
Residential [Member] | Home Equity [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		103,009	98,800
Residential [Member] | Home Equity [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile	[1]	796	556
Consumer [Member] | Consumer Direct [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		146,002	137,754
Consumer [Member] | Consumer Direct [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		145,966	137,692
Consumer [Member] | Consumer Direct [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile	[1]	36	62
Consumer [Member] | Consumer Indirect [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		530,542	489,667
Consumer [Member] | Consumer Indirect [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		529,897	489,019
Consumer [Member] | Consumer Indirect [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile	[1]	645	648
Residential and Consumer Portfolio Segments [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		1,564,153	1,503,705
Residential and Consumer Portfolio Segments [Member] | Performing [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile		1,551,829	1,487,362
Residential and Consumer Portfolio Segments [Member] | Nonperforming [Member]
Credit Risk Profile, Segregated by Class [Abstract]
Loan portfolio based on credit risk profile	[1]	$ 12,324	$ 16,343

[1] A loan is considered nonperforming if it is 90 days or more past due and/or on nonaccrual.