Revenue - Impact of Adoption on Balance Sheet (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
Amounts without ASC 606 impact
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Capitalized commissions, current	0
Total current assets	8,146
Capitalized commissions, long-term	0
Total assets	10,870
Accrued liabilities	1,011
Unearned revenue	9,807
Total current liabilities	14,640
Other liabilities	188
Long-term portion of unearned revenue	2,242
Total liabilities	18,694
Accumulated deficit	(209,011)
Total stockholders' equity (deficit)	(7,824)
Total liabilities and stockholders' equity (deficit)	10,870
Accounting Standards Update 2014-09 | ASC 606 adoption impact
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)