Summary of Significant Accounting Policies (Revenue by Product) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018	Sep. 30, 2018
Disaggregation of Revenue [Line Items]
Revenue	$ 21,745	$ 18,623	$ 45,746	$ 42,659	$ 42,659
Broadband
Disaggregation of Revenue [Line Items]
Revenue	14,150	13,679	31,477	34,545
Chips
Disaggregation of Revenue [Line Items]
Revenue	3,501	2,895	7,716	5,046
Navigation
Disaggregation of Revenue [Line Items]
Revenue	$ 4,094	$ 2,049	$ 6,553	$ 3,068
Product Concentration Risk | Revenue from Contract with Customer
Disaggregation of Revenue [Line Items]
Concentration risk percentage	100.00%	100.00%	100.00%	100.00%
Product Concentration Risk | Revenue from Contract with Customer | Broadband
Disaggregation of Revenue [Line Items]
Concentration risk percentage	65.00%	73.00%	69.00%	81.00%
Product Concentration Risk | Revenue from Contract with Customer | Chips
Disaggregation of Revenue [Line Items]
Concentration risk percentage	16.00%	16.00%	17.00%	12.00%
Product Concentration Risk | Revenue from Contract with Customer | Navigation
Disaggregation of Revenue [Line Items]
Concentration risk percentage	19.00%	11.00%	14.00%	7.00%