Acquisition - Additional Information (Detail) (USD $)	12 Months Ended		1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	May 31, 2012 CommerceFirst Bancorp, inc.
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Business acquisition, percentage of common stock acquired			100.00%
Business acquisition percentage of common stock acquired in exchange of common stock			50.00%
Business acquisition, percentage of common stock acquired in exchange of cash			50.00%
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares			732,054
Business Acquisition, Cost of Acquired Entity, Cash Paid			$ 12,381,000
Business acquisition, cash consideration Paid Per Share			$ 13.60
Business Acquisition, Purchase Price Allocation, Assets Acquired			187,977,000
Business Acquisition Purchase Price Allocation Loans Receivable			165,762,000
Business Acquisition, Purchase Price Allocation, Liabilities Assumed			170,565,000
Business Acquisition Purchase Price Allocation Liabilities Assumed Deposits			169,921,000
Business acquisition, addition to Company's equity			13,000,000
Business Acquisition, Purchase Price Allocation, Goodwill Amount	7,992,000		8,000,000
Business acquisition, pro forma revenue, net of interest expense	172,900,000	167,700,000
Business acquisition, pro forma net income	$ 37,100,000	$ 35,900,000