Credit Quality Assessment (Credit Risk Rating Indicators for Each Segment of Commercial Loan Portfolio) (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	$ 3,288,865	$ 3,127,392
Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	409,795	390,781
Pass | Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	384,562	366,367
Special Mention | Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	8,212	8,835
Substandard | Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	17,021	15,579
Doubtful | Commercial
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	0	0
Commercial Portfolio Segment [Member]
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	1,971,050	1,847,159
Commercial Portfolio Segment [Member] | Pass
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	1,900,997	1,771,095
Commercial Portfolio Segment [Member] | Special Mention
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	17,198	21,133
Commercial Portfolio Segment [Member] | Substandard
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	52,855	54,931
Commercial Portfolio Segment [Member] | Doubtful
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	0	0
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	223,103	205,124
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	694,179	640,193
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	643,973	611,061
Commercial Real Estate Portfolio Segment | Pass | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	220,747	201,642
Commercial Real Estate Portfolio Segment | Pass | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	679,253	621,511
Commercial Real Estate Portfolio Segment | Pass | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	616,435	581,575
Commercial Real Estate Portfolio Segment | Special Mention | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	698	698
Commercial Real Estate Portfolio Segment | Special Mention | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	1,857	3,931
Commercial Real Estate Portfolio Segment | Special Mention | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	6,431	7,669
Commercial Real Estate Portfolio Segment | Substandard | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	1,658	2,784
Commercial Real Estate Portfolio Segment | Substandard | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	13,069	14,751
Commercial Real Estate Portfolio Segment | Substandard | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	21,107	21,817
Commercial Real Estate Portfolio Segment | Doubtful | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	0	0
Commercial Real Estate Portfolio Segment | Doubtful | Commercial Investor Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	0	0
Commercial Real Estate Portfolio Segment | Doubtful | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment [Line Items]
Total loans and leases	$ 0	$ 0