Nature of business and summary of significant accounting policies (Details Textual) (USD $)	6 Months Ended	12 Months Ended		6 Months Ended	12 Months Ended	6 Months Ended	12 Months Ended	3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended		12 Months Ended	6 Months Ended	12 Months Ended				6 Months Ended	12 Months Ended
	Jun. 30, 2013	Dec. 31, 2011	Dec. 31, 2012	Jun. 30, 2013 Series A Preferred Stock [Member]	Dec. 31, 2011 Series A Preferred Stock [Member]	Jun. 30, 2013 Common Stock [Member]	Dec. 31, 2011 Common Stock [Member] Contingency Consideration [Member]	Jun. 30, 2013 Common Stock [Member] Warrant [Member]	Jun. 30, 2013 Common Stock [Member] Warrant [Member]	Jun. 30, 2012 Common Stock [Member] Warrant [Member]	Jun. 30, 2013 Class B Units [Member]	Jun. 30, 2013 Class B Units [Member]	Jun. 30, 2012 Class B Units [Member]	Dec. 31, 2011 Class B Units [Member]	Jun. 30, 2013 Class B Units [Member] Contingency Consideration [Member]	Dec. 31, 2011 Class B Units [Member] Contingency Consideration [Member]	Dec. 31, 2012 Class B Units [Member] Contingency Consideration [Member] First Stock Target [Member]	Dec. 31, 2011 Class B Units [Member] Contingency Consideration [Member] First Stock Target [Member]	Dec. 31, 2011 Class B Units [Member] Contingency Consideration [Member] Second Stock Target [Member]	Jun. 30, 2013 Class B Units [Member] Contingency Consideration [Member] Third Stock Target [Member]	Dec. 31, 2012 Class B Units [Member] Contingency Consideration [Member] Third Stock Target [Member]	Dec. 31, 2011 Class B Units [Member] Contingency Consideration [Member] Third Stock Target [Member]
Payments For Reverse Merger Consideration		$ 22,086,000
Exchangeable Units Issued During Period														4,541,394
Number Of Shares Issued To Member In Connection With Merger					454,139.4
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount								5,456,300	5,456,300	5,456,300	2,340,000		3,900,000
Preferred Stock, Voting Rights					the right to cast 10 votes per share in all matters
Stock Units And Exchangeable Units Cancelled During Period Upon Conversion Of Shares				220,139.4
Number Of Exchangeable Units Exchanged For Shares During Period												2,201,394
Restricted certificates of deposit	673,000		673,000
Stock Issued During Period, Shares, Conversion of Units						2,201,394
Common Stock Shares Reserved For Future Issuance Targets Met							4,400,000									4,400,000	1,466,666.7	1,466,666.7	1,466,666.7	1,466,666.6	1,466,666.6	1,466,666.6
Common Stock Shares Reserved For Future Issuance Targets Met Trading Price																		$ 15.00	$ 17.50			$ 20.00
Common Stock Shares Reserved For Future Issuance Foregoing Targets Year One															2,200,000
Common Stock Shares Reserved For Future Issuance Foregoing Targets Year Two															2,200,000
Business Combination Contingent Consideration Arrangements Amount Earnings Year One															17,500,000
Business Combination Contingent Consideration Arrangements Amount Earnings Year Two															25,000,000
Business Combination Contingent Consideration Arrangements Amount Earnings Year Three	$ 30,000,000