Note 11 - Stockholders' equity (Detail) - Stock Option Plan (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Number of shares, Exercised during period	68,210	131,560
The 1989 Non-Qualified Stock Option Plan [Member]
Number of shares, Beginning balance outstanding	102,000	180,250
Number of shares, Granted during period	0	0
Number of shares, Exercised during period	60,100	78,250
Number of shares, Canceled during period	0	0
Number of shares, Ending balance outstanding	41,900	102,000
Number of shares, Exercisable	41,900	102,000
Weighted average exercise price per share, Beginning balance outstanding (in Dollars per share)	4.35	3.97
Weighted average exercise price per share, Granted during period (in Dollars per share)	0	0
Weighted average exercise price per share, Exercised during period (in Dollars per share)	0	0
Weighted average exercise price per share, Canceled during period (in Dollars per share)	0	0
Weighted average exercise price per share, Ending balance outstanding (in Dollars per share)	4.82	4.35
Weighted average exercise price per share, Exercisable (in Dollars per share)	4.82	4.35
The 2001 Non-Qualified Stock Option Plan [Member]
Number of shares, Beginning balance outstanding	170,590	211,300
Number of shares, Granted during period	0	14,000
Number of shares, Exercised during period	8,110	53,310
Number of shares, Canceled during period	0	1,400
Number of shares, Ending balance outstanding	162,480	170,590
Number of shares, Exercisable	124,980	120,590
Weighted average exercise price per share, Beginning balance outstanding (in Dollars per share)	4.41	4.02
Weighted average exercise price per share, Granted during period (in Dollars per share)	4.25	4.25
Weighted average exercise price per share, Exercised during period (in Dollars per share)	0	0
Weighted average exercise price per share, Canceled during period (in Dollars per share)	0	0
Weighted average exercise price per share, Ending balance outstanding (in Dollars per share)	4.35	4.41
Weighted average exercise price per share, Exercisable (in Dollars per share)	4.27	4.32
The 2007 Share Incentive Plan [Member]
Number of shares, Beginning balance outstanding	200	200
Number of shares, Granted during period	0	0
Number of shares, Exercised during period	0	0
Number of shares, Canceled during period	0	0
Number of shares, Ending balance outstanding	200	200
Number of shares, Exercisable	200	200
Weighted average exercise price per share, Granted during period (in Dollars per share)	11.51
Weighted average exercise price per share, Ending balance outstanding (in Dollars per share)	11.51
Weighted average exercise price per share, Exercisable (in Dollars per share)	11.51