Derivative Instruments and Hedging Activities - Value of Derivative Assets and Derivative Liabilities (Detail) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	$ 11,295	$ 12,981
Fair value, Derivatives (included in Other Liabilities)	11,276	12,953
Collateral posted, Derivatives (included in Other Liabilities)	12,573	12,059
Other Assets | Interest Rate Swap Contracts-Commercial Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	11,295	12,981
Notional amount, Derivatives (included in Other Assets)	245,595	245,152
Other Assets | Interest Rate Lock Commitments-Mortgage Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	261	235
Notional amount, Derivatives (included in Other Assets)	9,894	8,822
Other Assets | Forward Sale Contracts-Mortgage Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	0	0
Notional amount, Derivatives (included in Other Assets)	0	0
Other Liabilities | Interest Rate Swap Contracts-Commercial Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	11,276	12,953
Notional amount, Derivatives (included in Other Liabilities)	245,595	245,152
Collateral posted, Derivatives (included in Other Liabilities)	12,753	12,059
Other Liabilities | Forward Sale Contracts-Mortgage Loans
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	5	57
Notional amount, Derivatives (included in Other Liabilities)	$ 9,800	$ 7,789