Loans and Loans Held for Sale - Composition of Loans (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Composition of the loans
Commercial loans	$ 2,892,522	$ 2,593,880
Consumer loans	976,224	972,319
Total Portfolio Loans	3,868,746	3,566,199
Loans held for sale	2,970us-gaap_LoansReceivableHeldForSaleNet	2,136us-gaap_LoansReceivableHeldForSaleNet
Total Loans	3,871,716us-gaap_LoansReceivableNet	3,568,335us-gaap_LoansReceivableNet
Commercial Real Estate [Member]
Composition of the loans
Commercial loans	1,682,236	1,607,756
Total Portfolio Loans	1,682,236	1,607,756
Commercial and Industrial [Member]
Composition of the loans
Commercial loans	994,138	842,449
Total Portfolio Loans	994,138	842,449
Commercial Construction [Member]
Composition of the loans
Commercial loans	216,148	143,675
Total Portfolio Loans	216,148	143,675
Residential Mortgage [Member]
Composition of the loans
Consumer loans	489,586	487,092
Total Portfolio Loans	489,586	487,092
Home Equity [Member]
Composition of the loans
Consumer loans	418,563	414,195
Total Portfolio Loans	418,563	414,195
Installment and Other Consumer [Member]
Composition of the loans
Consumer loans	65,567	67,883
Total Portfolio Loans	65,567	67,883
Consumer Construction [Member]
Composition of the loans
Consumer loans	2,508	3,149
Total Portfolio Loans	$ 2,508	$ 3,149

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Reflects the aggregate gross carrying amount of all commercial loans and leases held in portfolio, prior to deducting deferred income and the allowance for losses on commercial loans and leases.

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Reflects the aggregate gross carrying amount of all consumer loans and leases held in portfolio, prior to deducting deferred income and the allowance for losses on consumer loans and leases.

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

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Amount classified as loans attributable to disposal group held for sale or disposed of. Excludes loans and leases covered under loss sharing agreements and loans classified as debt securities.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes loans held for sale. Excludes loans and leases covered under loss sharing agreements.

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