Stock Based Compensation - Stock-based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Obligation with Joint and Several Liability Arrangement [Line Items]
Total stock-based compensation expense included in selling, general and administrative expense	$ 4,251	$ 2,706	$ 1,039
Cost of sales - contracts
Obligation with Joint and Several Liability Arrangement [Line Items]
Total stock-based compensation expense included in selling, general and administrative expense	367	234	90
Selling, general and administrative
Obligation with Joint and Several Liability Arrangement [Line Items]
Total stock-based compensation expense included in selling, general and administrative expense	$ 3,884	$ 2,472	$ 949