Credit Quality Assessment (Credit Quality of Loan Portfolio) (Detail) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Financing Receivable Recorded Investment Past Due [Line Items]
31-60 days	$ 9,663,000	$ 11,923,000
61-90 days	3,979,000	4,066,000
> 90 days	0	1,000
Total past due	13,642,000	15,990,000
Non-accrual loans and leases	28,530,000	30,574,000
Loans aquired with deteriorated credit quality	3,011,000	4,300,000
Current loans	3,082,209,000	2,733,402,000
Total loans and leases	3,127,392,000	2,784,266,000
Commercial
Financing Receivable Recorded Investment Past Due [Line Items]
31-60 days	759,000	382,000
61-90 days	995,000	1,142,000
> 90 days	0	0
Total past due	1,754,000	1,524,000
Non-accrual loans and leases	3,184,000	3,400,000
Loans aquired with deteriorated credit quality	1,238,000	1,363,000
Current loans	384,605,000	350,364,000
Total loans and leases	390,781,000	356,651,000
Leases
Financing Receivable Recorded Investment Past Due [Line Items]
31-60 days	11,000	4,000
61-90 days	0	0
> 90 days	0	0
Total past due	11,000	4,000
Non-accrual loans and leases	0	0
Loans aquired with deteriorated credit quality	0	0
Current loans	43,000	699,000
Total loans and leases	54,000	703,000
Consumer
Financing Receivable Recorded Investment Past Due [Line Items]
31-60 days	797,000	716,000
61-90 days	179,000	176,000
> 90 days	0	1,000
Total past due	976,000	893,000
Non-accrual loans and leases	1,668,000	2,259,000
Loans aquired with deteriorated credit quality	0	0
Current loans	422,908,000	370,505,000
Total loans and leases	425,552,000	373,657,000
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable Recorded Investment Past Due [Line Items]
31-60 days	0	0
61-90 days	320,000	0
> 90 days	0	0
Total past due	320,000	0
Non-accrual loans and leases	2,464,000	4,127,000
Loans aquired with deteriorated credit quality	0	0
Current loans	202,340,000	156,569,000
Total loans and leases	205,124,000	160,696,000
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable Recorded Investment Past Due [Line Items]
31-60 days	2,374,000	5,826,000
61-90 days	1,493,000	0
> 90 days	0	0
Total past due	3,867,000	5,826,000
Non-accrual loans and leases	8,156,000	6,802,000
Loans aquired with deteriorated credit quality	0	571,000
Current loans	628,170,000	538,979,000
Total loans and leases	640,193,000	552,178,000
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable Recorded Investment Past Due [Line Items]
31-60 days	2,658,000	876,000
61-90 days	156,000	2,540,000
> 90 days	0	0
Total past due	2,814,000	3,416,000
Non-accrual loans and leases	8,941,000	5,936,000
Loans aquired with deteriorated credit quality	1,773,000	2,366,000
Current loans	597,533,000	581,105,000
Total loans and leases	611,061,000	592,823,000
Residential Real Estate Portfolio Segment | Residential Mortgage
Financing Receivable Recorded Investment Past Due [Line Items]
31-60 days	3,064,000	4,119,000
61-90 days	836,000	208,000
> 90 days	0	0
Total past due	3,900,000	4,327,000
Non-accrual loans and leases	3,012,000	5,735,000
Loans aquired with deteriorated credit quality	0	0
Current loans	710,974,000	608,319,000
Total loans and leases	717,886,000	618,381,000
Residential Real Estate Portfolio Segment | Residential Construction
Financing Receivable Recorded Investment Past Due [Line Items]
31-60 days	0	0
61-90 days	0	0
> 90 days	0	0
Total past due	0	0
Non-accrual loans and leases	1,105,000	2,315,000
Loans aquired with deteriorated credit quality	0	0
Current loans	135,636,000	126,862,000
Total loans and leases	$ 136,741,000	$ 129,177,000