Summary of Significant Accounting Policies (Revenue by Product) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 24,300	$ 17,219	$ 21,745	$ 24,001	$ 25,241	$ 17,717	$ 18,623	$ 24,036	$ 87,265	$ 85,617	$ 122,895
Broadband
Disaggregation of Revenue [Line Items]
Revenue									53,233	68,418	109,633
Chips
Disaggregation of Revenue [Line Items]
Revenue									10,828	10,050	9,170
Navigation
Disaggregation of Revenue [Line Items]
Revenue									$ 23,204	$ 7,149	$ 4,092
Product Concentration Risk | Revenue from Contract with Customer
Disaggregation of Revenue [Line Items]
Concentration risk percentage									100.00%	100.00%	100.00%
Product Concentration Risk | Revenue from Contract with Customer | Broadband
Disaggregation of Revenue [Line Items]
Concentration risk percentage									61.00%	80.00%	89.00%
Product Concentration Risk | Revenue from Contract with Customer | Chips
Disaggregation of Revenue [Line Items]
Concentration risk percentage									12.00%	12.00%	8.00%
Product Concentration Risk | Revenue from Contract with Customer | Navigation
Disaggregation of Revenue [Line Items]
Concentration risk percentage									27.00%	8.00%	3.00%