Credit Risk Rating Indicators for Each Segment of Commercial Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	$ 2,475,078	$ 2,239,692
Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	334,040	260,327
Commercial Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	1,508,709	1,315,297
Commercial Portfolio Segment | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	334,040	260,327
Commercial Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	151,620	160,946
Commercial Portfolio Segment | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	443,237	371,948
Commercial Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	579,812	522,076
Commercial Portfolio Segment | Pass
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	1,351,991	1,162,633
Commercial Portfolio Segment | Pass | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	295,638	225,048
Commercial Portfolio Segment | Pass | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	132,375	137,181
Commercial Portfolio Segment | Pass | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	393,946	331,095
Commercial Portfolio Segment | Pass | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	530,032	469,309
Commercial Portfolio Segment | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	61,304	42,453
Commercial Portfolio Segment | Special Mention | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	12,731	8,551
Commercial Portfolio Segment | Special Mention | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	2,366	2,207
Commercial Portfolio Segment | Special Mention | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	20,789	9,592
Commercial Portfolio Segment | Special Mention | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	25,418	22,103
Commercial Portfolio Segment | Substandard
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	92,969	109,203
Commercial Portfolio Segment | Substandard | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	24,325	25,720
Commercial Portfolio Segment | Substandard | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	16,879	21,558
Commercial Portfolio Segment | Substandard | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	28,502	31,261
Commercial Portfolio Segment | Substandard | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	23,263	30,664
Commercial Portfolio Segment | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	2,445	1,008
Commercial Portfolio Segment | Doubtful | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	1,346	1,008
Commercial Portfolio Segment | Doubtful | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Loans and leases	$ 1,099