Earnings (loss) per share (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Numerator:
Net income (loss) attributable to the Company	$ 109,289	$ 503,714	$ (499,591)	$ 506,899
Denominator:
Weighted-average shares outstanding - Basic and diluted	13,582,106	13,582,106	13,582,106	13,582,106
Earnings (loss) per common share - Basic and diluted	$ 0.01	$ 0.04	$ (0.04)	$ 0.04
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation	612,500	727,500	612,500	727,500
Stock Options [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation	565,000		565,000
Warrant [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation	47,500		47,500