Derivatives - Fair Values of Derivative Instruments on Balance Sheet (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Derivatives, Fair Value [Line Items]
Derivative Fair Value Of Asset	$ 16,012	$ 15,579
Derivative Fair Value Of Liability	16,440	15,006
Derivatives not designated as hedging instruments [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	940,396	763,568
Derivative Fair Value Of Asset	16,012	15,579
Derivative Fair Value Of Liability	16,440	15,006
Derivatives not designated as hedging instruments [Member] | Interest rate swaps [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	753,382	650,667
Derivative Fair Value Of Asset	14,585	14,147
Derivative Fair Value Of Liability	14,974	13,777
Derivatives not designated as hedging instruments [Member] | Risk participation agreements [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	80,989	19,736
Derivative Fair Value Of Asset	105	2
Derivative Fair Value Of Liability	156	2
Derivatives not designated as hedging instruments [Member] | Forward commitments to sell residential mortgage loans [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	40,873	45,910
Derivative Fair Value Of Asset	56	326
Derivative Fair Value Of Liability	640	115
Derivatives not designated as hedging instruments [Member] | Interest rate-lock commitments on residential mortgage loans [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	28,025	25,956
Derivative Fair Value Of Asset	595	56
Derivative Fair Value Of Liability	27	107
Derivatives not designated as hedging instruments [Member] | Foreign exchange forward contracts [Member]
Derivatives, Fair Value [Line Items]
Notional Amount	37,127	21,299
Derivative Fair Value Of Asset	671	1,048
Derivative Fair Value Of Liability	$ 643	$ 1,005