Concentrations (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Concentrations
Number of areas in which operations are concentrated			1
Two government customers
Concentrations
Number of customers	2	2
One individual commercial customer
Concentrations
Number of customers	1	1
Total revenues | Customer | U.S. Government
Concentrations
Percentage of revenue	34.30%	38.00%	35.20%	32.90%
Total revenues | Customer | Two government customers
Concentrations
Percentage of revenue	26.10%	33.50%
Total revenues | Customer | One individual commercial customer
Concentrations
Percentage of revenue	64.00%	59.40%