Credit Quality Assessment (Recorded Investment with Respect to Impaired loans, Associated Allowance by Applicable Portfolio Segment and Principal Balance of Impaired Loans prior to Amounts Charged-off) (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	$ 10,587,000	$ 11,411,000
Impaired loans without a specific allowance	20,617,000	18,008,000
Impaired loans	31,204,000	29,419,000
Impaired Financing Receivable, Related Allowance	2,650,000	2,894,000
Unpaid principal balance in total impaired loans	44,792,000	42,185,000
Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	8,973,000	9,104,000
Impaired loans without a specific allowance	11,102,000	8,676,000
Impaired loans	20,075,000	17,780,000
Restructuring | Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	675,000	687,000
Impaired loans without a specific allowance	4,771,000	4,810,000
Impaired loans	5,446,000	5,497,000
Restructuring | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	939,000	1,620,000
Impaired loans without a specific allowance	4,744,000	4,522,000
Impaired loans	5,683,000	6,142,000
Commercial
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	2,358,000	1,468,000
Impaired loans without a specific allowance	2,502,000	2,426,000
Impaired loans	4,860,000	3,894,000
Impaired Financing Receivable, Related Allowance	1,058,000	788,000
Unpaid principal balance in total impaired loans	6,354,000	5,360,000
Commercial | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	1,459,000	473,000
Impaired loans without a specific allowance	1,126,000	1,115,000
Impaired loans	2,585,000	1,588,000
Commercial | Restructuring | Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	675,000	687,000
Impaired loans without a specific allowance	19,000	23,000
Impaired loans	694,000	710,000
Commercial | Restructuring | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	224,000	308,000
Impaired loans without a specific allowance	1,357,000	1,288,000
Impaired loans	1,581,000	1,596,000
All Other
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	0	0
Impaired loans without a specific allowance	3,813,000	3,841,000
Impaired loans	3,813,000	3,841,000
Impaired Financing Receivable, Related Allowance	0	0
Unpaid principal balance in total impaired loans	4,117,000	4,126,000
All Other | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	0	0
Impaired loans without a specific allowance	0	0
Impaired loans	0	0
All Other | Restructuring | Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	0	0
Impaired loans without a specific allowance	2,641,000	2,664,000
Impaired loans	2,641,000	2,664,000
All Other | Restructuring | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	0	0
Impaired loans without a specific allowance	1,172,000	1,177,000
Impaired loans	1,172,000	1,177,000
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	48,000	1,330,000
Impaired loans without a specific allowance	1,315,000	1,134,000
Impaired loans	1,363,000	2,464,000
Impaired Financing Receivable, Related Allowance	48,000	741,000
Unpaid principal balance in total impaired loans	6,662,000	7,044,000
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	48,000	1,330,000
Impaired loans without a specific allowance	563,000	0
Impaired loans	611,000	1,330,000
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction | Restructuring | Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	0	0
Impaired loans without a specific allowance	0	0
Impaired loans	0	0
Commercial Real Estate Portfolio Segment | Commercial Acquisition, Development and Construction | Restructuring | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	0	0
Impaired loans without a specific allowance	752,000	1,134,000
Impaired loans	752,000	1,134,000
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	2,401,000	2,364,000
Impaired loans without a specific allowance	9,793,000	7,915,000
Impaired loans	12,194,000	10,279,000
Impaired Financing Receivable, Related Allowance	545,000	541,000
Unpaid principal balance in total impaired loans	16,851,000	14,926,000
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	2,328,000	2,288,000
Impaired loans without a specific allowance	7,682,000	5,792,000
Impaired loans	10,010,000	8,080,000
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate | Restructuring | Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	0	0
Impaired loans without a specific allowance	2,111,000	2,123,000
Impaired loans	2,111,000	2,123,000
Commercial Real Estate Portfolio Segment | Commercial Investor Real Estate | Restructuring | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	73,000	76,000
Impaired loans without a specific allowance	0	0
Impaired loans	73,000	76,000
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	5,780,000	6,249,000
Impaired loans without a specific allowance	3,194,000	2,692,000
Impaired loans	8,974,000	8,941,000
Impaired Financing Receivable, Related Allowance	999,000	824,000
Unpaid principal balance in total impaired loans	10,808,000	10,729,000
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	5,138,000	5,013,000
Impaired loans without a specific allowance	1,731,000	1,769,000
Impaired loans	6,869,000	6,782,000
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate | Restructuring | Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	0	0
Impaired loans without a specific allowance	0	0
Impaired loans	0	0
Commercial Real Estate Portfolio Segment | Commercial Owner Occupied Real Estate | Restructuring | Non Accrual Loans
Financing Receivable Impaired [Line Items]
Impaired loans with a specific allowance	642,000	1,236,000
Impaired loans without a specific allowance	1,463,000	923,000
Impaired loans	$ 2,105,000	$ 2,159,000