Credit Risk Rating Indicators for Each Segment of Commercial Loan Portfolio (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	$ 2,605,458	$ 2,531,128
Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	334,979	346,708
Commercial Portfolio Segment
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,558,911	1,527,039
Commercial Portfolio Segment | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	334,979	346,708
Commercial Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	163,309	151,933
Commercial Portfolio Segment | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	497,365	456,888
Commercial Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	563,258	571,510
Commercial Portfolio Segment | Pass
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	1,424,845	1,373,442
Commercial Portfolio Segment | Pass | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	295,187	305,348
Commercial Portfolio Segment | Pass | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	154,813	141,802
Commercial Portfolio Segment | Pass | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	454,886	405,448
Commercial Portfolio Segment | Pass | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	519,959	520,844
Commercial Portfolio Segment | Special Mention
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	38,607	54,621
Commercial Portfolio Segment | Special Mention | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	18,816	13,603
Commercial Portfolio Segment | Special Mention | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	117	1,793
Commercial Portfolio Segment | Special Mention | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	2,893	21,963
Commercial Portfolio Segment | Special Mention | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	16,781	17,262
Commercial Portfolio Segment | Substandard
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	95,101	95,927
Commercial Portfolio Segment | Substandard | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	20,661	26,091
Commercial Portfolio Segment | Substandard | Commercial Acquisition, Development and Construction
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	8,379	8,338
Commercial Portfolio Segment | Substandard | Commercial Investor Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	39,543	28,885
Commercial Portfolio Segment | Substandard | Commercial Owner Occupied Real Estate
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	26,518	32,613
Commercial Portfolio Segment | Doubtful
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	358	3,049
Commercial Portfolio Segment | Doubtful | Commercial
Financing Receivable, Recorded Investment [Line Items]
Total loans and leases	315	1,666
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