Revenue - Opening Balance Sheet Adjustment (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Oct. 01, 2018	Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized commissions, current	$ 459	$ 580	$ 0
Prepaid expenses and other current assets	968		941
Total current assets	10,600	11,405	10,825
Capitalized commissions, long-term	129	112	0
Total assets	13,324	14,275	13,583
Accrued liabilities	1,595	1,611	1,609
Unearned revenue	8,301	10,721	11,645
Total current liabilities	13,154	15,668	16,590
Other liabilities	174	200	202
Long-term portion of unearned revenue	2,329	1,616	1,691
Total liabilities	20,422	19,042	20,041
Accumulated deficit	(209,002)	(205,728)	(207,419)
Total stockholders' equity (deficit)	(7,098)	(4,767)	(6,458)
Total liabilities and stockholders' equity (deficit)	13,324	14,275	$ 13,583
ASC 606 adoption adjustments | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized commissions, current	(459)
Prepaid expenses and other current assets	0
Total current assets	(459)
Capitalized commissions, long-term	(129)
Total assets	(588)
Accrued liabilities	(2)
Unearned revenue	777
Total current liabilities	775
Other liabilities	2
Long-term portion of unearned revenue	74
Total liabilities	851
Accumulated deficit	(1,439)
Total stockholders' equity (deficit)	(1,439)
Total liabilities and stockholders' equity (deficit)	$ (588)
ASC 606 Adoption Adjustments | ASC 606 adoption adjustments | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized commissions, current		580
Total current assets		580
Capitalized commissions, long-term		112
Total assets		692
Accrued liabilities		2
Unearned revenue		(924)
Total current liabilities		(922)
Other liabilities		(2)
Long-term portion of unearned revenue		(75)
Total liabilities		(999)
Accumulated deficit		1,691
Total stockholders' equity (deficit)		1,691
Total liabilities and stockholders' equity (deficit)		$ 692