Credit Risk Rating Indicators for Each Segment of Commercial Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 2,662,010	$ 2,531,128
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	332,670	346,708
Pass | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	292,973	305,348
Special Mention | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	19,345	13,603
Substandard | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	20,063	26,091
Doubtful | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	289	1,666
Commercial Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,578,788	1,527,039
Commercial Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	158,739	151,933
Commercial Portfolio Segment | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	518,029	456,888
Commercial Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	569,350	571,510
Commercial Portfolio Segment | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,466,652	1,373,442
Commercial Portfolio Segment | Pass | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	151,546	141,802
Commercial Portfolio Segment | Pass | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	493,523	405,448
Commercial Portfolio Segment | Pass | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	528,610	520,844
Commercial Portfolio Segment | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	38,467	54,621
Commercial Portfolio Segment | Special Mention | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	109	1,793
Commercial Portfolio Segment | Special Mention | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,713	21,963
Commercial Portfolio Segment | Special Mention | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	17,300	17,262
Commercial Portfolio Segment | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	73,337	95,927
Commercial Portfolio Segment | Substandard | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	7,084	8,338
Commercial Portfolio Segment | Substandard | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	22,750	28,885
Commercial Portfolio Segment | Substandard | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	23,440	32,613
Commercial Portfolio Segment | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	332	3,049
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	43	592
Commercial Portfolio Segment | Doubtful | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 0	$ 791