Credit Risk Rating Indicators for Each Segment of Commercial Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 2,531,128	$ 2,239,692
Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	346,708	260,327
Commercial Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,527,039	1,315,297
Commercial Portfolio Segment | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	346,708	260,327
Commercial Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	151,933	160,946
Commercial Portfolio Segment | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	456,888	371,948
Commercial Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	571,510	522,076
Commercial Portfolio Segment | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,374,262	1,162,633
Commercial Portfolio Segment | Pass | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	305,348	225,048
Commercial Portfolio Segment | Pass | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	141,802	137,181
Commercial Portfolio Segment | Pass | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	405,448	331,095
Commercial Portfolio Segment | Pass | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	520,844	469,309
Commercial Portfolio Segment | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	54,621	42,453
Commercial Portfolio Segment | Special Mention | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	13,603	8,551
Commercial Portfolio Segment | Special Mention | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,793	2,207
Commercial Portfolio Segment | Special Mention | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	21,963	9,592
Commercial Portfolio Segment | Special Mention | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	17,262	22,103
Commercial Portfolio Segment | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	95,107	109,203
Commercial Portfolio Segment | Substandard | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	26,091	25,720
Commercial Portfolio Segment | Substandard | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	8,338	21,558
Commercial Portfolio Segment | Substandard | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	28,885	31,261
Commercial Portfolio Segment | Substandard | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	32,613	30,664
Commercial Portfolio Segment | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	3,049	1,008
Commercial Portfolio Segment | Doubtful | Commercial Loan
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,666	1,008
Commercial Portfolio Segment | Doubtful | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	0	0
Commercial Portfolio Segment | Doubtful | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	592	0
Commercial Portfolio Segment | Doubtful | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 791	$ 0