Stockholders’ Equity - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended
	Apr. 30, 2018	Apr. 24, 2001	Mar. 31, 2018	Mar. 31, 2017	Apr. 24, 2018	Dec. 31, 2017	Dec. 31, 2000
Class of Stock [Line Items]
Common stock, shares authorized (in shares)			190,000,000			190,000,000
Common stock, shares issued (in shares)			3,056,000			2,979,000
Common stock, shares outstanding (in shares)			3,056,000			2,979,000
Common stock valuation (in dollars per share)			$ 10
Intrinsic value of options exercised			$ 678	$ 34
Proceeds from the exercise of options			61	$ 61
Compensation cost related to nonvested awards not yet recognized			$ 2,829
2000 Plan
Class of Stock [Line Items]
Shares of common stock reserved for issuance							17,200,000
2001 Plan
Class of Stock [Line Items]
Shares of common stock reserved for issuance			9,000,000			9,000,000
Options granted, term		10 years
Vested options, exercise period		3 months
2001 Plan | Minimum
Class of Stock [Line Items]
Vesting period		4 years
2001 Plan | Maximum
Class of Stock [Line Items]
Vesting period		5 years
Stock options to purchase common stock | 2001 Plan
Class of Stock [Line Items]
Number of shares available for issuance (in shares)			1,300,000			1,700,000
Subsequent Event
Class of Stock [Line Items]
Shares of common stock issued upon conversion (in shares)	24,600,000
Subsequent Event | 2001 Plan
Class of Stock [Line Items]
Number of shares available for issuance (in shares)					0