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, 2012	Dec. 31, 2011
Impaired loans	$ 57,577	$ 67,575
Allowance	4,886	7,791
Unpaid principal balance in total impaired loans	79,833	82,600
Non Accrual Loans
Impaired loans	32,612	40,467
Restructuring | Accrual Loans
Impaired loans	8,285	6,881
Restructuring | Non Accrual Loans
Impaired loans	16,680	20,227
Commercial Loan
Impaired loans	7,739	9,092
Allowance	753	1,037
Unpaid principal balance in total impaired loans	10,102	11,303
Commercial Loan | Non Accrual Loans
Impaired loans	2,711	4,526
Commercial Loan | Restructuring | Accrual Loans
Impaired loans	2,475	1,866
Commercial Loan | Restructuring | Non Accrual Loans
Impaired loans	2,553	2,700
All Other
Impaired loans	5,670	7,402
Allowance	1,548	1,595
All Other | Non Accrual Loans
Impaired loans	221	1,893
All Other | Restructuring | Accrual Loans
Impaired loans	4,277	4,308
All Other | Restructuring | Non Accrual Loans
Impaired loans	1,172	1,201
Impaired Financing Receivables with Related Allowance
Impaired loans	22,669	36,742
Impaired Financing Receivables with Related Allowance | Non Accrual Loans
Impaired loans	7,974	20,106
Impaired Financing Receivables with Related Allowance | Restructuring | Accrual Loans
Impaired loans	6,311	5,528
Impaired Financing Receivables with Related Allowance | Restructuring | Non Accrual Loans
Impaired loans	8,384	11,108
Impaired Financing Receivables with Related Allowance | Commercial Loan
Impaired loans	2,573	2,763
Impaired Financing Receivables with Related Allowance | Commercial Loan | Non Accrual Loans
Impaired loans	848	1,110
Impaired Financing Receivables with Related Allowance | Commercial Loan | Restructuring | Accrual Loans
Impaired loans	1,527	1,346
Impaired Financing Receivables with Related Allowance | Commercial Loan | Restructuring | Non Accrual Loans
Impaired loans	198	307
Impaired Financing Receivables with Related Allowance | All Other
Impaired loans	4,051	4,955
Impaired Financing Receivables with Related Allowance | All Other | Non Accrual Loans
Impaired loans	221	1,093
Impaired Financing Receivables with Related Allowance | All Other | Restructuring | Accrual Loans
Impaired loans	3,453	3,475
Impaired Financing Receivables with Related Allowance | All Other | Restructuring | Non Accrual Loans
Impaired loans	377	387
Impaired Financing Receivables with No Related Allowance
Impaired loans	34,908	30,833
Impaired Financing Receivables with No Related Allowance | Non Accrual Loans
Impaired loans	24,638	20,361
Impaired Financing Receivables with No Related Allowance | Restructuring | Accrual Loans
Impaired loans	1,974	1,353
Impaired Financing Receivables with No Related Allowance | Restructuring | Non Accrual Loans
Impaired loans	8,296	9,119
Impaired Financing Receivables with No Related Allowance | Commercial Loan
Impaired loans	5,166	6,329
Impaired Financing Receivables with No Related Allowance | Commercial Loan | Non Accrual Loans
Impaired loans	1,863	3,416
Impaired Financing Receivables with No Related Allowance | Commercial Loan | Restructuring | Accrual Loans
Impaired loans	948	520
Impaired Financing Receivables with No Related Allowance | Commercial Loan | Restructuring | Non Accrual Loans
Impaired loans	2,355	2,393
Impaired Financing Receivables with No Related Allowance | All Other
Impaired loans	1,619	2,447
Impaired Financing Receivables with No Related Allowance | All Other | Non Accrual Loans
Impaired loans		800
Impaired Financing Receivables with No Related Allowance | All Other | Restructuring | Accrual Loans
Impaired loans	824	833
Impaired Financing Receivables with No Related Allowance | All Other | Restructuring | Non Accrual Loans
Impaired loans	795	814
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Impaired loans	13,055	18,701
Allowance	973	7
Unpaid principal balance in total impaired loans	32,652	37,442
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction | Non Accrual Loans
Impaired loans	5,073	7,798
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction | Restructuring | Non Accrual Loans
Impaired loans	7,982	10,903
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Impaired loans	14,143	16,964
Allowance	276	3,380
Unpaid principal balance in total impaired loans	17,986	17,389
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate | Non Accrual Loans
Impaired loans	12,947	15,695
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate | Restructuring | Non Accrual Loans
Impaired loans	1,196	1,269
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Impaired loans	16,970	15,416
Allowance	1,336	1,772
Unpaid principal balance in total impaired loans	19,093	16,466
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate | Non Accrual Loans
Impaired loans	11,660	10,555
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate | Restructuring | Accrual Loans
Impaired loans	1,533	707
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate | Restructuring | Non Accrual Loans
Impaired loans	3,777	4,154
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Acquisition, Development and Construction
Impaired loans	4,679	6,504
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Acquisition, Development and Construction | Restructuring | Non Accrual Loans
Impaired loans	4,679	6,504
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Investor Real Estate
Impaired loans	1,175	14,440
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Investor Real Estate | Non Accrual Loans
Impaired loans	996	13,812
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Investor Real Estate | Restructuring | Non Accrual Loans
Impaired loans	179	628
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Owner Occupied Real Estate
Impaired loans	10,191	8,080
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Owner Occupied Real Estate | Non Accrual Loans
Impaired loans	5,909	4,091
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Owner Occupied Real Estate | Restructuring | Accrual Loans
Impaired loans	1,331	707
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with Related Allowance | Commercial Owner Occupied Real Estate | Restructuring | Non Accrual Loans
Impaired loans	2,951	3,282
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Acquisition, Development and Construction
Impaired loans	8,376	12,197
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Acquisition, Development and Construction | Non Accrual Loans
Impaired loans	5,073	7,798
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Acquisition, Development and Construction | Restructuring | Non Accrual Loans
Impaired loans	3,303	4,399
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Investor Real Estate
Impaired loans	12,968	2,524
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Investor Real Estate | Non Accrual Loans
Impaired loans	11,951	1,883
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Investor Real Estate | Restructuring | Non Accrual Loans
Impaired loans	1,017	641
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Owner Occupied Real Estate
Impaired loans	6,779	7,336
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Owner Occupied Real Estate | Non Accrual Loans
Impaired loans	5,751	6,464
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Owner Occupied Real Estate | Restructuring | Accrual Loans
Impaired loans	202
Commercial Real Estate Portfolio Segment | Impaired Financing Receivables with No Related Allowance | Commercial Owner Occupied Real Estate | Restructuring | Non Accrual Loans
Impaired loans	$ 826	$ 872