Summary of Revenue from the Sale of Products and 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, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Disaggregation Of Revenue [Line Items]
Total revenue	$ 11,845	$ 13,910	$ 22,304	$ 27,184
Operating Segments
Disaggregation Of Revenue [Line Items]
Total revenue	11,845	13,910	22,304	27,184
Operating Segments | Oil and Gas Markets
Disaggregation Of Revenue [Line Items]
Total revenue	4,565	6,108	8,323	12,948
Operating Segments | Oil and Gas Markets | Traditional Exploration Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	3,261	2,490	5,987	6,089
Operating Segments | Oil and Gas Markets | Wireless Exploration Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	310	1,558	454	4,181
Operating Segments | Oil and Gas Markets | Reservoir Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	994	2,060	1,882	2,678
Operating Segments | Adjacent Markets
Disaggregation Of Revenue [Line Items]
Total revenue	7,234	7,802	13,847	14,236
Operating Segments | Adjacent Markets | Industrial Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	4,120	4,711	7,682	8,387
Operating Segments | Adjacent Markets | Imaging Product Revenue
Disaggregation Of Revenue [Line Items]
Total revenue	3,114	$ 3,091	6,165	$ 5,849
Operating Segments | Emerging Markets
Disaggregation Of Revenue [Line Items]
Total revenue	$ 46		$ 134