Leases - Additional Information (Details) $ in Thousands		1 Months Ended			3 Months Ended		6 Months Ended
	Jan. 21, 2020 renewal_term	Nov. 30, 2016 ft²	Oct. 31, 2014 renewal_term	May 31, 2013 ft² renewal_term	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Aug. 03, 2020 USD ($)	Jun. 30, 2020 USD ($)	Jul. 01, 2019 USD ($)	Jun. 01, 2018 ft²	Feb. 28, 2015 ft²
Leases [Line Items]
Accumulated deficit					$ (203,512)		$ (203,512)			$ (199,779)
Cash payments for operating leases					53	$ 96	123	$ 192
Cash payments for financing leases					3	$ 0	6	$ 0
1st Detect
Leases [Line Items]
Lease, expiration date			Apr. 30, 2020
Lessee, Operating Lease, Existence of Option to Extend [true false]			true
Number of renewal terms | renewal_term			2
Renewal term			5 years
Leased premises, right of first refusal exercised | ft²													9,138
Austin, Texas
Leases [Line Items]
Leased premises | ft²		5,219
Lease, expiration date		Dec. 31, 2023
Decrease in operating lease right-of-use asset									$ 506
Decrease in operating lease liability									$ 540
Webster, Texas
Leases [Line Items]
Lease, expiration date	Apr. 30, 2021
Decrease in operating lease right-of-use asset					171		171
Decrease in operating lease liability					$ 192		$ 192
Lessee, Operating Lease, Existence of Option to Extend [true false]	true
Number of renewal terms | renewal_term	1
Renewal term	1 year
Original lease area of land removed | ft²												8,118
Leased premises remaining area | ft²												17,560
Webster, Texas | 1st Detect | Research and Development and Production Facility
Leases [Line Items]
Leased premises | ft²				16,540
Lease, expiration date				Jun. 30, 2018
Lessee, Operating Lease, Existence of Option to Extend [true false]				true
Number of renewal terms | renewal_term				2
Renewal term				5 years
Lease term				62 months
Adjustment to Opening Retained Earnings Related to Adoption ASC Topic 842 | ASU 2016-02
Leases [Line Items]
Accumulated deficit											$ 230