Commitments and contingencies (Tables)

12 Months Ended

Dec. 31, 2012

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block]

Future minimum lease payments under these non-cancelable operating leases as of December 31, 2012 are as follows:

2013	$	1,199,008
2014		563,902
2015		461,979
2016		295,395
2017		248,179
Thereafter		3,681,324
	$	6,449,787