Accounts receivable and revenue concentrations (Details Textual)						3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended	3 Months Ended		6 Months Ended
	Jun. 30, 2012 Accounts Receivable [Member] Customer One [Member]	Jun. 30, 2011 Accounts Receivable [Member] Customer One [Member]	Jun. 30, 2012 Accounts Receivable [Member] Customer Two[Member]	Jun. 30, 2011 Accounts Receivable [Member] Customer Three [Member]	Jun. 30, 2011 Accounts Receivable [Member] Customer Six [Member]	Jun. 30, 2012 Sales Revenue, Services, Net [Member] Customer One [Member]	Jun. 30, 2012 Sales Revenue, Services, Net [Member] Customer One [Member]	Jun. 30, 2011 Sales Revenue, Services, Net [Member] Customer One [Member]	Jun. 30, 2012 Sales Revenue, Services, Net [Member] Customer Two[Member]	Jun. 30, 2012 Sales Revenue, Services, Net [Member] Customer Two[Member]	Jun. 30, 2011 Sales Revenue, Services, Net [Member] Customer Three [Member]	Jun. 30, 2011 Sales Revenue, Services, Net [Member] Customer Four [Member]	Jun. 30, 2011 Sales Revenue, Services, Net [Member] Customer Four [Member]	Jun. 30, 2011 Sales Revenue, Services, Net [Member] Customer Five [Member]	Jun. 30, 2011 Sales Revenue, Services, Net [Member] Customer Six [Member]	Jun. 30, 2011 Sales Revenue, Services, Net [Member] Customer Six [Member]
Concentration Risk [Line Items]
Concentration risk percentage of gross receivables	24.00%	26.00%	57.00%	29.00%	33.00%
Concentration risk, percentage of total revenue						16.00%	7.00%	10.00%	33.00%	15.00%	11.00%	11.00%	12.00%	13.00%	23.00%	12.00%