Earnings per share - Weighted Average Number of Shares Used in Computing Earnings Per Share (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share, Diluted, by Common Class, Including Two Class Method [Line Items]
Basic earnings per share	4,816,859	2,610,856
Effect of dilutive securities:
Stock options	2,484	1,931
Diluted earnings per share	4,819,343	2,612,787
Basic earnings per share	$ 0.25	$ 0.27
Diluted earnings per share	$ 0.25	$ 0.27