Recorded Investment with Respect to Impaired loans, Associated Allowance by Applicable Portfolio Segment and Principal Balance of Impaired Loans prior to Amounts Charged-off (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Impaired loans	$ 38,809	$ 48,773
Allowance	4,313	5,149
Unpaid principal balance in total impaired loans	58,478	73,333
Non Accrual Loans
Impaired loans	19,521	28,699
Restructuring | Accrual Loans
Impaired loans	8,213	10,110
Restructuring | Non Accrual Loans
Impaired loans	11,075	9,964
Commercial
Impaired loans	6,723	8,984
Allowance	1,397	2,597
Unpaid principal balance in total impaired loans	9,742	11,506
Commercial | Non Accrual Loans
Impaired loans	2,846	4,360
Commercial | Restructuring | Accrual Loans
Impaired loans	2,240	4,373
Commercial | Restructuring | Non Accrual Loans
Impaired loans	1,637	251
All Other
Impaired loans	6,599	6,430
Allowance	1,450	1,180
Unpaid principal balance in total impaired loans	7,184	6,904
All Other | Non Accrual Loans
Impaired loans	0	0
All Other | Restructuring | Accrual Loans
Impaired loans	3,525	4,234
All Other | Restructuring | Non Accrual Loans
Impaired loans	3,074	2,196
Impaired Financing Receivables with Related Allowance
Impaired loans	15,646	27,526
Impaired Financing Receivables with Related Allowance | Non Accrual Loans
Impaired loans	3,770	17,052
Impaired Financing Receivables with Related Allowance | Restructuring | Accrual Loans
Impaired loans	4,388	7,903
Impaired Financing Receivables with Related Allowance | Restructuring | Non Accrual Loans
Impaired loans	7,488	2,571
Impaired Financing Receivables with Related Allowance | Commercial
Impaired loans	2,600	5,723
Impaired Financing Receivables with Related Allowance | Commercial | Non Accrual Loans
Impaired loans	1,368	2,514
Impaired Financing Receivables with Related Allowance | Commercial | Restructuring | Accrual Loans
Impaired loans	994	2,981
Impaired Financing Receivables with Related Allowance | Commercial | Restructuring | Non Accrual Loans
Impaired loans	238	228
Impaired Financing Receivables with Related Allowance | All Other
Impaired loans	4,664	4,723
Impaired Financing Receivables with Related Allowance | All Other | Non Accrual Loans
Impaired loans	0	0
Impaired Financing Receivables with Related Allowance | All Other | Restructuring | Accrual Loans
Impaired loans	2,389	3,419
Impaired Financing Receivables with Related Allowance | All Other | Restructuring | Non Accrual Loans
Impaired loans	2,275	1,304
Impaired Financing Receivables with No Related Allowance
Impaired loans	23,163	21,247
Impaired Financing Receivables with No Related Allowance | Non Accrual Loans
Impaired loans	15,751	11,647
Impaired Financing Receivables with No Related Allowance | Restructuring | Accrual Loans
Impaired loans	3,825	2,207
Impaired Financing Receivables with No Related Allowance | Restructuring | Non Accrual Loans
Impaired loans	3,587	7,393
Impaired Financing Receivables with No Related Allowance | Commercial
Impaired loans	4,123	3,261
Impaired Financing Receivables with No Related Allowance | Commercial | Non Accrual Loans
Impaired loans	1,478	1,846
Impaired Financing Receivables with No Related Allowance | Commercial | Restructuring | Accrual Loans
Impaired loans	1,246	1,392
Impaired Financing Receivables with No Related Allowance | Commercial | Restructuring | Non Accrual Loans
Impaired loans	1,399	23
Impaired Financing Receivables with No Related Allowance | All Other
Impaired loans	1,935	1,707
Impaired Financing Receivables with No Related Allowance | All Other | Non Accrual Loans
Impaired loans	0	0
Impaired Financing Receivables with No Related Allowance | All Other | Restructuring | Accrual Loans
Impaired loans	1,136	815
Impaired Financing Receivables with No Related Allowance | All Other | Restructuring | Non Accrual Loans
Impaired loans	799	892
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Impaired loans	5,885	6,332
Allowance	817	0
Unpaid principal balance in total impaired loans	15,918	21,590
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction | Non Accrual Loans
Impaired loans	3,519	3,033
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction | Restructuring | Accrual Loans
Impaired loans	0	0
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction | Restructuring | Non Accrual Loans
Impaired loans	2,366	3,299
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Impaired loans	12,593	11,843
Allowance	167	774
Unpaid principal balance in total impaired loans	16,622	15,405
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate | Non Accrual Loans
Impaired loans	11,106	10,796
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate | Restructuring | Accrual Loans
Impaired loans	852	0
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate | Restructuring | Non Accrual Loans
Impaired loans	635	1,047
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Impaired loans	7,009	15,184
Allowance	482	598
Unpaid principal balance in total impaired loans	9,012	17,928
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate | Non Accrual Loans
Impaired loans	2,050	10,510
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate | Restructuring | Accrual Loans
Impaired loans	1,596	1,503
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate | Restructuring | Non Accrual Loans
Impaired loans	3,363	3,171
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Acquisition, Development and Construction
Impaired loans	3,764	0
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Acquisition, Development and Construction | Non Accrual Loans
Impaired loans	1,398	0
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Acquisition, Development and Construction | Restructuring | Accrual Loans
Impaired loans	0	0
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Acquisition, Development and Construction | Restructuring | Non Accrual Loans
Impaired loans	2,366	0
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Investor Real Estate
Impaired loans	790	10,219
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Investor Real Estate | Non Accrual Loans
Impaired loans	790	10,219
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Investor Real Estate | Restructuring | Accrual Loans
Impaired loans	0	0
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Investor Real Estate | Restructuring | Non Accrual Loans
Impaired loans	0	0
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Owner Occupied Real Estate
Impaired loans	3,828	6,861
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Owner Occupied Real Estate | Non Accrual Loans
Impaired loans	214	4,319
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Owner Occupied Real Estate | Restructuring | Accrual Loans
Impaired loans	1,005	1,503
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Owner Occupied Real Estate | Restructuring | Non Accrual Loans
Impaired loans	2,609	1,039
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Acquisition, Development and Construction
Impaired loans	2,121	6,332
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Acquisition, Development and Construction | Non Accrual Loans
Impaired loans	2,121	3,033
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Acquisition, Development and Construction | Restructuring | Accrual Loans
Impaired loans	0	0
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Acquisition, Development and Construction | Restructuring | Non Accrual Loans
Impaired loans	0	3,299
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Investor Real Estate
Impaired loans	11,803	1,624
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Investor Real Estate | Non Accrual Loans
Impaired loans	10,316	577
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Investor Real Estate | Restructuring | Accrual Loans
Impaired loans	852	0
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Investor Real Estate | Restructuring | Non Accrual Loans
Impaired loans	635	1,047
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Owner Occupied Real Estate
Impaired loans	3,181	8,323
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Owner Occupied Real Estate | Non Accrual Loans
Impaired loans	1,836	6,191
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Owner Occupied Real Estate | Restructuring | Accrual Loans
Impaired loans	591	0
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Owner Occupied Real Estate | Restructuring | Non Accrual Loans
Impaired loans	$ 754	$ 2,132