Loans (Details 2) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	$ 1,859,266	$ 1,745,960	$ 1,725,536
Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	880,295	861,716	840,044
Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	538,412	484,058	526,573
Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	440,559	400,186	358,919
Originated Loans [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	1,800,685	1,675,329	1,652,031
Originated Loans [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	865,025	840,752	817,667
Originated Loans [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	536,239	480,944	522,340
Originated Loans [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	399,421	353,633	312,024
Originated Loans [Member] | Performing [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	1,780,073	1,647,131	1,616,325
Originated Loans [Member] | Performing [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	849,385	818,044	789,338
Originated Loans [Member] | Performing [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	535,277	479,237	519,409
Originated Loans [Member] | Performing [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	395,411	349,850	307,578
Originated Loans [Member] | Nonperforming [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	20,612	28,198	35,706
Originated Loans [Member] | Nonperforming [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	15,640	22,708	28,329
Originated Loans [Member] | Nonperforming [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	962	1,707	2,931
Originated Loans [Member] | Nonperforming [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	4,010	3,783	4,446
Acquired Loans [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	58,581	70,631	73,505
Acquired Loans [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	15,270	20,964	22,377
Acquired Loans [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	2,173	3,114	4,233
Acquired Loans [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	41,138	46,553	46,895
Acquired Loans [Member] | Performing [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	57,975	68,592	72,094
Acquired Loans [Member] | Performing [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	14,928	19,387	21,517
Acquired Loans [Member] | Performing [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	2,173	3,114	4,233
Acquired Loans [Member] | Performing [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	40,874	46,091	46,344
Acquired Loans [Member] | Nonperforming [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	606	2,039	1,411
Acquired Loans [Member] | Nonperforming [Member] | Real estate residential [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	342	1,577	860
Acquired Loans [Member] | Nonperforming [Member] | Consumer installment [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	0	0	0
Acquired Loans [Member] | Nonperforming [Member] | Home equity [Member]
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Recorded investment (loan balance), Consumer, Total	$ 264	$ 462	$ 551