Revenue - Opening Balance Sheet Adjustment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Oct. 01, 2018	Sep. 30, 2018
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized commissions, current	$ 509	$ 580	$ 0
Prepaid expenses and other current assets	858		941
Total current assets	8,655	11,405	10,825
Capitalized commissions, long-term	114	112	0
Total assets	11,493	14,275	13,583
Accrued liabilities	1,013	1,611	1,609
Unearned revenue	9,009	10,721	11,645
Total current liabilities	13,844	15,668	16,590
Other liabilities	186	200	202
Long-term portion of unearned revenue	2,168	1,616	1,691
Total liabilities	17,822	19,042	20,041
Accumulated deficit	(207,516)	(205,728)	(207,419)
Total stockholders' equity (deficit)	(6,329)	(4,767)	(6,458)
Total liabilities and stockholders' equity (deficit)	11,493	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	(509)
Total current assets	(509)
Capitalized commissions, long-term	(114)
Total assets	(623)
Accrued liabilities	(2)
Unearned revenue	798
Total current liabilities	796
Other liabilities	2
Long-term portion of unearned revenue	74
Total liabilities	872
Accumulated deficit	(1,495)
Total stockholders' equity (deficit)	(1,495)
Total liabilities and stockholders' equity (deficit)	$ (623)
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