Fair Values of Financial Instruments - Estimated Fair Values of Financial Instruments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Assets:
Investment securities available for sale	$ 536,201	$ 513,343
Investment securities held to maturity	560,847	378,174
Carrying Amount
Assets:
Cash and cash equivalents	109,434	101,460
Interest-bearing time deposits	55,069	38,443
Investment securities available for sale	536,201	513,343
Investment securities held to maturity	559,378	361,020
Mortgage loans held for sale	5,331	22,300
Loans	3,564,539	2,832,843
FRB and FHLB stock	38,990	32,785
Interest rate swap asset	4,009	6,300
Interest receivable	18,672	16,367
Liabilities:
Deposits	4,231,468	3,346,383
Borrowings:
Federal funds purchased	125,645	18,862
Securities sold under repurchase agreements	148,672	141,828
FHLB Advances	122,140	94,238
Subordinated debentures and term loans	126,807	112,161
Interest rate swap liability	3,953	9,766
Interest payable	1,771	1,841
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	109,434	101,460
Interest-bearing time deposits	55,069	38,443
Liabilities:
Deposits	3,082,117	2,478,706
Significant Other Observable Inputs (Level 2)
Assets:
Investment securities available for sale	526,224	495,015
Investment securities held to maturity	525,998	366,590
Mortgage loans held for sale	5,331	22,300
FRB and FHLB stock	38,990	32,785
Interest rate swap asset	4,009	6,300
Interest receivable	18,672	16,367
Liabilities:
Deposits	934,937	865,793
Borrowings:
Federal funds purchased	125,645	18,862
Securities sold under repurchase agreements	148,852	142,318
FHLB Advances	122,962	97,357
Subordinated debentures and term loans	82,607	62,133
Interest rate swap liability	3,953	9,766
Interest payable	1,771	1,841
Significant Unobservable Inputs (Level 3)
Assets:
Investment securities available for sale	9,977	18,328
Investment securities held to maturity	34,849	11,584
Loans	$ 3,506,615	$ 2,852,614