v3.10.0.1
Debt (Details)
Sep. 30, 2018
USD ($)
agreement
Dec. 31, 2017
USD ($)
Lines of Credit    
Aggregate borrowing base $ 25,000,000.0  
Amount outstanding 0 $ 0
Security deposit $ 15,000,000  
Government Grants    
Number of conditional loan agreements (in agreements) | agreement 2  
Amount of loan $ 3,500,000 3,500,000
Prince George's County, Maryland    
Government Grants    
Loan interest rate 3.00%  
Department of Commerce    
Government Grants    
Loan interest rate 3.00%  
Standby letters of credit    
Lines of Credit    
Aggregate borrowing base $ 10,000,000.0  
Revolving working capital facility | Short Course Segment    
Lines of Credit    
Aggregate borrowing base   $ 1,900,000.0