Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) - shares shares in Thousands		3 Months Ended		12 Months Ended
	Apr. 01, 2016	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Concentration Risk [Line Items]
Securities excluded from net loss per share calculation (in shares)		90	137
Warranty service periods	10 years
Minimum
Concentration Risk [Line Items]
Warranty service periods		1 year
Maximum
Concentration Risk [Line Items]
Warranty service periods		5 years
Geographic concentration risk | United States
Concentration Risk [Line Items]
Concentration risk (less than for one percent)		98.00%		98.00%
Revenue | Geographic concentration risk | Countries outside of the United States
Concentration Risk [Line Items]
Concentration risk (less than for one percent)		1.00%	2.00%
Commercial Lighting Retrofit Company | Revenue | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk (less than for one percent)		10.00%
Commercial Lighting Retrofit Company | Accounts receivable | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk (less than for one percent)		13.00%		17.00%
Distributor To The U.S. Navy | Revenue | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk (less than for one percent)		46.00%	14.00%
Distributor To The U.S. Navy | Accounts receivable | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk (less than for one percent)		47.00%		39.00%
Global Healthcare Systems, Northeast Ohio | Revenue | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk (less than for one percent)			22.00%
Global Healthcare Systems, Northeast Ohio | Accounts receivable | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk (less than for one percent)		10.00%		21.00%
Huntington Ingalls, Incorporated | Revenue | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk (less than for one percent)			10.00%
U.S. Navy | Revenue | Customer concentration risk
Concentration Risk [Line Items]
Concentration risk (less than for one percent)		50.00%	24.00%