Derivative Instruments and Hedging Activities - Value of Derivative Assets and Derivative Liabilities (Detail) (Not Designated as Hedging Instruments [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	$ 12,125	$ 13,698
Fair value, Derivatives (included in Other Liabilities)	12,103	13,647
Other Assets [Member] | Interest Rate Swap Contracts-Commercial Loans [Member]
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	12,125	13,698
Notional amount, Derivatives (included in Other Assets)	249,159	261,754
Collateral posted	0	0
Other Assets [Member] | Interest Rate Lock Commitments - Mortgage Loans [Member]
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	187	85
Notional amount, Derivatives (included in Other Assets)	7,854	3,989
Other Assets [Member] | Forward Sale Contracts-Mortgage Loans [Member]
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Assets)	0	34
Notional amount, Derivatives (included in Other Assets)	0	5,250
Other Liabilities [Member] | Interest Rate Swap Contracts-Commercial Loans [Member]
Derivatives not Designated as Hedging Instruments
Collateral posted	11,492	12,611
Fair value, Derivatives (included in Other Liabilities)	12,103	13,647
Notional amount, Derivatives (included in Other Liabilities)	249,159	261,754
Other Liabilities [Member] | Interest Rate Lock Commitments - Mortgage Loans [Member]
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	0	0
Notional amount, Derivatives (included in Other Liabilities)	0	0
Other Liabilities [Member] | Forward Sale Contracts-Mortgage Loans [Member]
Derivatives not Designated as Hedging Instruments
Fair value, Derivatives (included in Other Liabilities)	10	0
Notional amount, Derivatives (included in Other Liabilities)	$ 7,948	$ 0