Revenue Recognition - Summary of Revenue from the Sale of Products and Performance of Services Under Contracts with Customers Excludes All Revenue Earned from Rental Contracts by Operating Segments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Disaggregation Of Revenue [Line Items]
Total revenue	$ 9,517	$ 11,845	$ 18,600	$ 22,304
Operating Segments
Disaggregation Of Revenue [Line Items]
Total revenue	9,517	11,845	18,600	22,304
Operating Segments | Oil and Gas Markets
Disaggregation Of Revenue [Line Items]
Total revenue	2,073	4,565	4,987	8,323
Operating Segments | Oil and Gas Markets | Traditional Exploration Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	1,257	3,261	3,587	5,987
Operating Segments | Oil and Gas Markets | Wireless Exploration Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	479	310	883	454
Operating Segments | Oil and Gas Markets | Reservoir Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	337	994	517	1,882
Operating Segments | Adjacent Markets
Disaggregation Of Revenue [Line Items]
Total revenue	7,072	7,234	13,144	13,847
Operating Segments | Adjacent Markets | Industrial Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	4,186	4,120	7,782	7,682
Operating Segments | Adjacent Markets | Imaging Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	2,886	3,114	5,362	6,165
Operating Segments | Emerging Markets
Disaggregation Of Revenue [Line Items]
Total revenue	$ 372	$ 46	$ 469	$ 134