Loans, Credit Risk Profile Based on Rating Category and Payment Activity and on Performing and Nonperforming Status, Segregated by Class (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	$ 1,325,491		$ 1,303,767
Residential real estate and consumer loan portfolio based on performing and nonperforming status	1,226,046		1,252,781
Commercial Construction [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	115,091		120,577
Commercial Secured By Real Estate [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	820,925		798,887
Commercial Other [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	379,308		374,597
Equipment Lease [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	10,167		9,706
Real Estate Construction [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	54,431		53,534
Real Estate Mortgage [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	664,329		650,075
Home Equity [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	82,724		84,841
Consumer Direct [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	126,005		123,949
Consumer Indirect [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	298,557		340,382
Pass [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	1,091,036		1,062,375
Pass [Member] | Commercial Construction [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	86,482		85,886
Pass [Member] | Commercial Secured By Real Estate [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	672,486		643,312
Pass [Member] | Commercial Other [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	321,901		323,471
Pass [Member] | Equipment Lease [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	10,167		9,706
Watch [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	133,364		134,517
Watch [Member] | Commercial Construction [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	13,041		17,721
Watch [Member] | Commercial Secured By Real Estate [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	80,318		78,611
Watch [Member] | Commercial Other [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	40,005		38,185
Watch [Member] | Equipment Lease [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	0		0
OAEM [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	24,958		24,134
OAEM [Member] | Commercial Construction [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	1,067		1,379
OAEM [Member] | Commercial Secured By Real Estate [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	19,798		21,087
OAEM [Member] | Commercial Other [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	4,093		1,668
OAEM [Member] | Equipment Lease [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	0		0
Substandard [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	61,977		62,385
Substandard [Member] | Commercial Construction [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	7,301		8,783
Substandard [Member] | Commercial Secured By Real Estate [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	42,792		46,238
Substandard [Member] | Commercial Other [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	11,884		7,364
Substandard [Member] | Equipment Lease [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	0		0
Doubtful [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	14,156		20,356
Doubtful [Member] | Commercial Construction [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	7,200		6,808
Doubtful [Member] | Commercial Secured By Real Estate [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	5,531		9,639
Doubtful [Member] | Commercial Other [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	1,425		3,909
Doubtful [Member] | Equipment Lease [Member]
Credit risk profile, segregated by class [Line Items]
Commercial loan portfolio based on credit risk profile	0		0
Performing [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	1,217,627		1,244,146
Performing [Member] | Real Estate Construction [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	53,824		52,911
Performing [Member] | Real Estate Mortgage [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	657,635		643,152
Performing [Member] | Home Equity [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	82,114		84,306
Performing [Member] | Consumer Direct [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	125,896		123,878
Performing [Member] | Consumer Indirect [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	298,158		339,899
Nonperforming [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	8,419	[1]	8,635	[1]
Nonperforming [Member] | Real Estate Construction [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	607	[1]	623	[1]
Nonperforming [Member] | Real Estate Mortgage [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	6,694	[1]	6,923	[1]
Nonperforming [Member] | Home Equity [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	610	[1]	535	[1]
Nonperforming [Member] | Consumer Direct [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	109	[1]	71	[1]
Nonperforming [Member] | Consumer Indirect [Member]
Credit risk profile, segregated by class [Line Items]
Residential real estate and consumer loan portfolio based on performing and nonperforming status	$ 399	[1]	$ 483	[1]

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