Concentrations (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Concentrations
Number of areas in which operations are concentrated			1
Two government customers
Concentrations
Number of customers	2
One government customer
Concentrations
Number of customers		1
One individual commercial customer
Concentrations
Number of customers	1	1
Total revenues | Customer | U.S. Government
Concentrations
Percentage of revenue	30.60%	28.20%	35.60%	28.50%
Total revenues | Customer | Two government customers
Concentrations
Percentage of revenue	27.90%
Total revenues | Customer | One government customer
Concentrations
Percentage of revenue		28.10%
Total revenues | Customer | One individual commercial customer
Concentrations
Percentage of revenue	67.70%	67.90%