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Allowance for Loan Losses - Recorded Investment in Consumer Loan Classes by Performing and Nonperforming Status (Details) - Consumer - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 1,257,855	$ 1,256,024
% of Total	100.00%	100.00%
Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 1,246,904	$ 1,242,559
% of Total	99.10%	98.90%
Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 10,951	$ 13,465
% of Total	0.90%	1.10%
Residential mortgage
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 698,774	$ 701,982
% of Total	100.00%	100.00%
Residential mortgage | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 691,609	$ 692,064
% of Total	99.00%	98.60%
Residential mortgage | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 7,165	$ 9,918
% of Total	1.00%	1.40%
Home equity
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 487,326	$ 482,284
% of Total	100.00%	100.00%
Home equity | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 483,611	$ 478,845
% of Total	99.20%	99.30%
Home equity | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 3,715	$ 3,439
% of Total	0.80%	0.70%
Installment and other consumer
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 67,204	$ 65,852
% of Total	100.00%	100.00%
Installment and other consumer | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 67,133	$ 65,744
% of Total	99.90%	99.80%
Installment and other consumer | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 71	$ 108
% of Total	0.10%	0.20%
Consumer construction
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 4,551	$ 5,906
% of Total	100.00%	100.00%
Consumer construction | Performing
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 4,551	$ 5,906
% of Total	100.00%	100.00%
Consumer construction | Nonperforming
Financing Receivable, Recorded Investment [Line Items]
Loans recorded investment	$ 0	$ 0
% of Total	0.00%	0.00%

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- Definition

Loans and leases receivable gross carrying amount consumer percentage.

+ References

No definition available.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Definition

Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=82891408&loc=d3e4428-111522

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