Revenue - Impact of Adoption on Statement of Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 7,997	$ 8,460	$ 15,499	$ 17,355
Cost of revenues	2,004	2,531	3,846	4,956
Gross margin	5,993	5,929	11,653	12,399
Selling and marketing (operating expenses)	3,836	3,867	7,779	7,977
Loss from operations	(1,123)	(1,259)	(2,777)	(2,225)
Loss before income taxes	(1,361)	(1,343)	(3,161)	(2,410)
Net loss	(1,486)	(1,449)	(3,274)	(1,129)
Net loss attributable to common stockholders	$ (1,531)	$ (1,499)	$ (3,372)	$ (1,251)
Loss per common share - basic (in usd per share)	$ (0.29)	$ (0.34)	$ (0.64)	$ (0.28)
Loss per common share – diluted (in usd per share)	$ (0.29)	$ (0.34)	$ (0.64)	$ (0.28)
Amounts without ASC 606 impact
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 8,017		$ 15,645
Cost of revenues	2,004		3,846
Gross margin	6,013		11,799
Selling and marketing (operating expenses)	3,801		7,674
Loss from operations	(1,068)		(2,526)
Loss before income taxes	(1,306)		(2,910)
Net loss	(1,431)		(3,023)
Net loss attributable to common stockholders	$ (1,476)		$ (3,121)
Loss per common share - basic (in usd per share)	$ (0.28)		$ (0.59)
Loss per common share – diluted (in usd per share)	$ (0.28)		$ (0.59)
Accounting Standards Update 2014-09 | ASC 606 adoption impact
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 20		$ 146
Cost of revenues	0		0
Gross margin	20		146
Selling and marketing (operating expenses)	(35)		(105)
Loss from operations	55		251
Loss before income taxes	55		251
Net loss	55		251
Net loss attributable to common stockholders	$ 55		$ 251
Loss per common share - basic (in usd per share)	$ 0.01		$ 0.05
Loss per common share – diluted (in usd per share)	$ 0.01		$ 0.05
Product and other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	$ 1,796	$ 2,690	$ 3,547	$ 5,713
Cost of revenues	645	$ 1,203	1,296	$ 2,426
Product and other | Amounts without ASC 606 impact
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	1,816		3,693
Cost of revenues	645		1,296
Product and other | Accounting Standards Update 2014-09 | ASC 606 adoption impact
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Revenues	20		146
Cost of revenues	$ 0		$ 0