Summary of Significant Accounting Policies (Revenue by Product) (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Disaggregation of Revenue [Line Items]
Revenue	$ 24,001	$ 24,036
Broadband
Disaggregation of Revenue [Line Items]
Revenue	17,327	20,866
Chips
Disaggregation of Revenue [Line Items]
Revenue	4,215	2,151
Navigation
Disaggregation of Revenue [Line Items]
Revenue	$ 2,459	$ 1,019
Product Concentration Risk | Revenue from Contract with Customer
Disaggregation of Revenue [Line Items]
Concentration risk percentage	100.00%	100.00%
Product Concentration Risk | Revenue from Contract with Customer | Broadband
Disaggregation of Revenue [Line Items]
Concentration risk percentage	72.00%	87.00%
Product Concentration Risk | Revenue from Contract with Customer | Chips
Disaggregation of Revenue [Line Items]
Concentration risk percentage	18.00%	9.00%
Product Concentration Risk | Revenue from Contract with Customer | Navigation
Disaggregation of Revenue [Line Items]
Concentration risk percentage	10.00%	4.00%