Stock-Based Compensation - Additional Information (Details)					1 Months Ended					12 Months Ended
	Jan. 01, 2018 shares	Aug. 31, 2016 USD ($) shares	Aug. 23, 2016 USD ($) $ / shares shares	Feb. 29, 2016 USD ($) shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 shares	May 31, 2015 shares	Jun. 30, 2014 shares	Jun. 30, 2010 USD ($) Period shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 shares	Dec. 31, 2014 shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period of replacement options			3 years
Options expired in relation to the offer			456,995
Options granted (in shares)			334,027
Shares eligible for purchase via options			113,531
Exercise price of replacement options | $ / shares			$ 7.20
Incremental charge resulting from the plan modification | $			$ 926,000
Amortization period of incremental charge			3 years
New Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Outstanding awards					0	0				0	0
Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unamortized compensation cost, net of expected forfeitures | $					$ 300,000					$ 300,000
Weighted average expected period over which the expense is to be recognized										9 months 18 days
Fair value of vested options and awards | $										$ 700,000
Tax benefits associated with exercise of stock options | $										$ 0	$ 0	$ 0
Dividend yield (as a percent)										0.00%	0.00%	0.00%
Stock options exercised										0	0	0
Employee stock purchase plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized and unissued					150,000					150,000
Number of shares reserved for issuance									200,000
Increase in number of shares reserved for issuance							200,000
Number of offering periods | Period									2
Offering period									6 months
Purchase price to be paid by participants as a percentage of price per share either at the beginning or the end of each six-month offering period, whichever is less									85.00%
Shares of common stock issued under the plan		31,900		37,300
Aggregate purchase price of shares issued | $		$ 167,000		$ 197,000
Employee stock purchase plan | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Maximum amount of shares that eligible employee may purchase annually (in dollars) | $									$ 25,000
RSU's
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unamortized compensation cost, net of expected forfeitures | $					$ 100,000					$ 100,000
Weighted average expected period over which the expense is to be recognized										3 months 18 days
Amended 2000 Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized and unissued					0					0
Equity Incentive Plan 2010
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares authorized and unissued					4,007,000	231,000				4,007,000	231,000	114,000	106,000
Number of shares reserved for issuance														400,000
Increase in number of shares reserved for issuance	50,000
Term of Plan										10 years
Options expired in relation to the offer												58,000
Options granted (in shares)										40,000	160,000	384,000
Equity Incentive Plan 2010 | Options
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Increase in number of shares reserved for issuance					4,000,000	200,000		150,000		4,050,000	250,000	50,000
Maximum annual option grants or other awards to the entity's non-employee directors (in shares)					40,000					40,000
Maximum one-time grant of an option or other awards to the entitiy's non employee directors (in shares) | $										$ 120,000
Maximum term of options granted										10 years
Minimum percentage of voting rights required for applicability of a specific expriation term					10.00%					10.00%
Maximum expiration term of options granted										5 years
Vesting period of replacement options										4 years
Equity Incentive Plan 2010 | Options | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of Plan										6 years
Equity Incentive Plan 2010 | Options | Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Term of Plan										10 years
Equity Incentive Plan 2010 | RSU's
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total intrinsic value of the RSUs outstanding | $					$ 100,000					$ 100,000