Allowance for Loan Losses and Credit Quality of Loans, Credit Quality by Loan Class (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Credit Quality by Loan Class [Abstract]
Net Loans	$ 6,887,709	$ 6,583,639
Consumer Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,284,563	2,235,437
Consumer Credit Exposure [Member] | Dealer Finance [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,216,144	1,227,870
Consumer Credit Exposure [Member] | Specialty Lending [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	524,928	438,866
Consumer Credit Exposure [Member] | Home Equity [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	474,566	498,179
Residential Real Estate Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,380,836	1,320,370
Originated Loans [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	6,565,118	6,181,948
Originated Loans [Member] | Commercial Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,589,349	2,359,639
Originated Loans [Member] | Commercial Credit Exposure [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,478,108	2,244,654
Originated Loans [Member] | Commercial Credit Exposure [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	25,242	63,336
Originated Loans [Member] | Commercial Credit Exposure [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	85,999	51,649
Originated Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	848,119
Originated Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	796,778
Originated Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	11,348
Originated Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	39,993
Originated Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,741,230
Originated Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,681,330
Originated Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	13,894
Originated Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	46,006
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		753,664
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		708,452
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		30,337
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		14,875
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,536,304
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,481,688
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		28,264
Originated Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		26,352
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		35,541
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		31,137
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,294
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,110
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		34,130
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		23,377
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,441
Originated Loans [Member] | Commercial Credit Exposure [Member] | Agricultural Real Estate [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		8,312
Originated Loans [Member] | Business Banking Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	489,271	480,880
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	476,052	468,823
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	13,219	12,057
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	489,271	480,880
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	476,052	468,823
Originated Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	13,219	12,057
Originated Loans [Member] | Consumer Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,252,939	2,191,531
Originated Loans [Member] | Consumer Credit Exposure [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,245,076	2,182,742
Originated Loans [Member] | Consumer Credit Exposure [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	7,863	8,789
Originated Loans [Member] | Consumer Credit Exposure [Member] | Dealer Finance [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,216,112
Originated Loans [Member] | Consumer Credit Exposure [Member] | Dealer Finance [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,212,955
Originated Loans [Member] | Consumer Credit Exposure [Member] | Dealer Finance [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	3,157
Originated Loans [Member] | Consumer Credit Exposure [Member] | Specialty Lending [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	524,928
Originated Loans [Member] | Consumer Credit Exposure [Member] | Specialty Lending [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	523,366
Originated Loans [Member] | Consumer Credit Exposure [Member] | Specialty Lending [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,562
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	511,899
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	508,755
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	3,144
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,665,518
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,659,911
Originated Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		5,607
Originated Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		458,307
Originated Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		455,230
Originated Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		3,077
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		67,706
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		67,601
Originated Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		105
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,233,559	1,149,898
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,225,599	1,142,649
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	7,960	7,249
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,233,559	1,149,898
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,225,599	1,142,649
Originated Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	7,960	7,249
Acquired Loans [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	322,591	401,691
Acquired Loans [Member] | Commercial Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	110,616	146,209
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	107,045	141,073
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,923	923
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	648	4,213
Acquired Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	26,124
Acquired Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	23,283
Acquired Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	2,831
Acquired Loans [Member] | Commercial Credit Exposure [Member] | C&I [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	10
Acquired Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	84,492
Acquired Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	83,762
Acquired Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	92
Acquired Loans [Member] | Commercial Credit Exposure [Member] | CRE [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	638
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		39,575
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		37,825
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		425
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,325
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		106,634
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Pass [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		103,248
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Special Mention [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		498
Acquired Loans [Member] | Commercial Credit Exposure [Member] | Commercial Real Estate [Member] | Substandard [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,888
Acquired Loans [Member] | Business Banking Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	33,074	41,104
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	29,945	38,236
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	3,129	2,868
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	33,074	41,104
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Non-classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	29,945	38,236
Acquired Loans [Member] | Business Banking Credit Exposure [Member] | Business Banking [Member] | Classified [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	3,129	2,868
Acquired Loans [Member] | Consumer Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	31,624	43,906
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	31,382	43,531
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	242	375
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Dealer Finance [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	32
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Dealer Finance [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	32
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Dealer Finance [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	0
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	31,592
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	31,350
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	242
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,218
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		1,195
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Indirect [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		23
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		39,872
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		39,544
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Home Equity [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		328
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,816
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		2,792
Acquired Loans [Member] | Consumer Credit Exposure [Member] | Direct [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans		24
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	147,277	170,472
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	145,779	168,901
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	1,498	1,571
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	147,277	170,472
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member] | Performing [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	145,779	168,901
Acquired Loans [Member] | Residential Real Estate Credit Exposure [Member] | Residential Real Estate [Member] | Nonperforming [Member]
Credit Quality by Loan Class [Abstract]
Net Loans	$ 1,498	$ 1,571