Stockholders' Equity and Stock-based Compensation - Narrative (Details)						1 Months Ended	12 Months Ended			14 Months Ended	69 Months Ended
	Dec. 14, 2017 $ / shares shares	Dec. 22, 2016 USD ($)	Mar. 01, 2016 individual $ / shares shares	Feb. 04, 2016	Mar. 01, 2015 individual $ / shares shares	Dec. 31, 2017 USD ($) Person $ / shares shares	Dec. 31, 2017 USD ($) Person $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Feb. 29, 2016 USD ($) shares	Nov. 04, 2015 USD ($)	Dec. 31, 2014 shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding options under the stock option plans (in shares)						890,341	890,341	847,635	560,797	847,635			599,069
Shares available for future grant and issuance						488,403	488,403	599,720	97,003	599,720			183,468
Maximum number of shares available for sale through ATM Program | $		$ 20,000,000.0
Stock repurchase amount, authorized amount | $						$ 25,000,000	$ 25,000,000					$ 25,000,000
Shares repurchased, value | $								$ 964,000	$ 1,989,000	$ 3,000,000
Number of shares repurchased										451,792
Repurchased shares, average price per share (usd per share) | $ / shares										$ 6.41
Reverse stock split ratio of one share				0.066667
Common stock, shares authorized						26,666,667	26,666,667	26,666,667		26,666,667
Common stock, par value (usd per share) | $ / shares						$ 0.01	$ 0.01	$ 0.01		$ 0.01
Total intrinsic value of options exercised | $							$ 100,000	$ 100,000	100,000
Cash received from option exercises | $							$ 100,000	$ 0	$ 0
Weighted average grant date fair value for stock option awards (usd per share) | $ / shares							$ 8.10	$ 2.04	$ 16.65
Purchase price of common stock, percentage of price							85.00%
Exercise of stock options, Shares							15,000
Term of common stock used in determining market-based implied volatility							6 months
Equity Investment Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock purchased to restricted stock issued, ratio						0.2
Equity Investment Program | Executive officers and other key employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, award vesting period in years							90 days
Number of common stock shares sold (in shares)	219,346
Equity Investment Program | Private placement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of common stock shares sold (in shares)	120,567
Price per share of common stock share sold (usd per share) | $ / shares	$ 13.05
Stock options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, award vesting period in years							4 years
Stock options, term in years							10 years
Restricted stock and restricted stock unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, award vesting period in years							3 years
Intrinsic value of restricted stock and restricted stock unit awards | $						$ 4,000,000	$ 4,000,000
Weighted average grant date fair value for restricted stock and restricted stock unit awards (usd per share) | $ / shares							$ 11.36	$ 3.81	$ 34.20
Total fair value of shares vested | $							$ 600,000	$ 200,000	$ 600,000
Employee stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Minimum payroll deductions at base compensation under employee stock purchase plan											1.00%
Maximum payroll deductions at base compensation under employee stock purchase plan											10.00%
Maximum purchase limit of shares for each participant per offering period											33
Maximum purchase limit of shares for each participant annually											66
Maximum purchase limit of shares on the basis of fair market value on offering date, for each participant in any calendar year | $											$ 10,000
Offering period											6 months
Company recorded compensation expense | $								$ 100,000	$ 200,000
Stock appreciation rights (SARs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares outstanding options under the stock option plans (in shares)						565,864	565,864	1,416,133	216,532	1,416,133			9,333
Stock options, award vesting period in years			4 years		4 years
Stock options, term in years							10 years
Weighted average grant date fair value for stock option awards (usd per share) | $ / shares								$ 17.55	$ 9.94
Company recorded compensation expense | $							$ 6,600,000	$ 500,000	$ 100,000
Percentage of fair market value of shares for calculation of exercise price SAR							100.00%
Number of awards issued during period			1,210,000		207,207
Number of individuals that received SARs | individual			15		16
Exercise price of awards issued during period | $ / shares			$ 3.1		$ 34.20
Number of days volume-weighted average price of stock measured for vesting					20 days
Exercise of stock options, Shares							713,330
Percentage of shares allowed to be exercised annually, if vested			33.33%		33.33%
Number of vested and outstanding stock appreciation rights						9,333	9,333
Number of individuals holding stock appreciation rights awards | Person						1	1
Weighted average exercise price of stock appreciation rights awards | $ / shares						$ 45.00	$ 45.00
Stock appreciation rights (SARs) | Equity Investment Program
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Exercise of stock options, Shares							663,330
Participants gain on exercises of awards (usd per share) | $ / shares							$ 9.95
Stock appreciation rights (SARs) | First one-third of awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage			33.33%		33.33%
Percentage that weighted average price of common stock must be greater than exercise price of SARs			120.00%		120.00%
Stock appreciation rights (SARs) | Second one-third of awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage			33.33%		33.33%
Percentage that weighted average price of common stock must be greater than exercise price of SARs			125.00%		125.00%
Stock appreciation rights (SARs) | Final one-third of awards
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual vesting percentage			33.33%		33.33%
Percentage that weighted average price of common stock must be greater than exercise price of SARs			130.00%		130.00%