Accounts receivable and revenue concentrations (Details Textual)	3 Months Ended		9 Months Ended									6 Months Ended		9 Months Ended	6 Months Ended	9 Months Ended
	Sep. 30, 2012 Customer	Sep. 30, 2011 Customer	Sep. 30, 2012 Customer	Sep. 30, 2011 Customer	Sep. 30, 2012 Accounts Receivable [Member] Customer One [Member]	Sep. 30, 2012 Accounts Receivable [Member] Customer Two[Member]	Sep. 30, 2011 Accounts Receivable [Member] Customer Two[Member]	Sep. 30, 2011 Accounts Receivable [Member] Customer Three [Member]	Sep. 30, 2011 Accounts Receivable [Member] Customer Four [Member]	Sep. 30, 2012 Accounts Receivable [Member] Customer Five [Member]	Sep. 30, 2012 Accounts Receivable [Member] Customer Six [Member]	Sep. 30, 2012 Sales Revenue, Services, Net [Member] Customer One [Member]	Sep. 30, 2012 Sales Revenue, Services, Net [Member] Customer Two[Member]	Sep. 30, 2012 Sales Revenue, Services, Net [Member] Customer Two[Member]	Sep. 30, 2011 Sales Revenue, Services, Net [Member] Customer Three [Member]	Sep. 30, 2011 Sales Revenue, Services, Net [Member] Customer Three [Member]	Sep. 30, 2012 Sales Revenue, Services, Net [Member] Customer Five [Member]	Sep. 30, 2012 Sales Revenue, Services, Net [Member] Customer Seven [Member]
Concentration Risk [Line Items]
Concentration risk percentage of gross receivables					13.00%	22.00%	13.00%	63.00%	11.00%	33.00%	10.00%
Concentration risk, percentage of total revenue												14.00%	28.00%	12.00%	66.00%	37.00%	10.00%	25.00%
Number of Company's largest customers, receivables	4	3	4	3
Number of Company's largest customers, revenue	2	1	3	1