Summary of Significant Accounting Policies - Additional Information (Details)				1 Months Ended		3 Months Ended	12 Months Ended
	Feb. 28, 2022 USD ($)	Aug. 31, 2021 USD ($)	Feb. 28, 2021 USD ($) $ / shares shares	Jul. 31, 2021 USD ($) $ / shares shares	Feb. 28, 2021 USD ($) $ / shares shares	Sep. 30, 2020 Employee	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($) Employee $ / shares shares	Dec. 31, 2019 USD ($) $ / shares shares	Jan. 31, 2022 USD ($)	Aug. 03, 2021 USD ($)	Jul. 15, 2021 USD ($)	May 31, 2020 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Net loss							$ (12,944,000)	$ (14,051,000)
Accumulated deficit							(304,107,000)	$ (291,163,000)
Cash, cash equivalents and restricted cash							47,057,000
Aggregate gross sales price		$ 22,800,000									$ 22,800,000	$ 40,000,000
Common stock sold under agreement | shares | shares					1,186,000			2,726,000	658,000
Offering costs					$ 157,000		1,538,000	$ 463,000	$ 210,000
Weighted average sales price (in dollars per share) | $ / shares					$ 2.68			$ 2.92	$ 2.82
Net proceeds from common stock sold					$ 3,025,000		41,642,000	$ 7,500,000	$ 1,643,000
Allowance for potential customer revenue credits							131,000	437,000
Payments to develop software							1,290,000	1,869,000
Amortization of capitalized costs							2,356,000	2,984,000
Unamortized internally developed software costs, including construction in progress							3,029,000	4,008,000
Uncertain tax position							0	0
Impairment of long-lived assets held-for-use							0	0
Advertising and promotion expense							221,000	90,000
Aggregate foreign currency (losses) gains							$ (21,000)	(21,000)
At-the-market Offering [Member]
Summary Of Significant Accounting Policies [Line Items]
Aggregate gross sales price		50,000,000									50,000,000
Accounting Standards Update 2019-12 [Member]
Summary Of Significant Accounting Policies [Line Items]
Accounting standards update, adopted [true false]							true
Accounting standards update, adoption date							Jan. 01, 2021
Accounting standards update, immaterial effect [true false]							true
Software and Software Development Costs [Member]
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, useful life							3 years
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member]
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents, fair value disclosure							$ 44,930,000	$ 12,386,000
Google [Member] | Accounts Receivable [Member] | Customer Concentration Risk [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration risk							39.00%	34.00%
Google [Member] | Sales Revenue, Net [Member] | Customer Concentration Risk [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of concentration risk							35.00%	31.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Aggregate gross sales price							$ 50,000,000				100,000,000
Offering costs		$ 100,000,000
JMP Securities [Member]
Summary Of Significant Accounting Policies [Line Items]
Aggregate gross sales price				$ 40,000,000
Paycheck Protection Program [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Aggregate principal amount of the loan										$ 3,117,000
Paycheck Protection Program [Member] | Harvest Small Business Finance, LLC [Member]
Summary Of Significant Accounting Policies [Line Items]
Aggregate principal amount of the loan													$ 3,320,000
Paycheck Protection Program [Member] | Harvest Small Business Finance, LLC [Member] | Subsequent Event [Member]
Summary Of Significant Accounting Policies [Line Items]
Debt instrument expected loan forgiveness										$ 3,117,000
Repayment of loan	$ 200,000
Restructuring and Reduction in Force Plan [Member] | 2020 Restructuring Plan [Member]
Summary Of Significant Accounting Policies [Line Items]
Expected reduction of workforce | Employee						60		60
2021 Equity Distribution Agreement [Member]
Summary Of Significant Accounting Policies [Line Items]
Common stock sold under agreement | shares | shares			1,186,000	4,316,000				2,726,000	658,000
Offering costs			$ 157,000	$ 1,200,000				$ 463,000	$ 210,000
Weighted average sales price (in dollars per share) | $ / shares			$ 2.68	$ 9.27				$ 2.92	$ 2.82
Net proceeds from common stock sold			$ 3,025,000	$ 38,800,000				$ 7,500,000	$ 1,643,000
2021 Equity Distribution Agreement [Member] | JMP Securities [Member]
Summary Of Significant Accounting Policies [Line Items]
Aggregate gross sales price											$ 50,000,000
Net of securities fees				$ 1,200,000
2021 Equity Distribution Agreement [Member] | JMP Securities [Member] | Maximum [Member] | At-the-market Offering [Member]
Summary Of Significant Accounting Policies [Line Items]
Aggregate gross sales price												$ 40,000,000