Stockholders' Equity (Options) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Nov. 03, 2014	Apr. 30, 2007
Stockholders' Equity
Number of shares available for future grants	549,073
Stock options
Number of options
Balance at the beginning of period (in shares)	2,786,977
Options granted (in shares)	90,000
Options exercised (in shares)	(289,931)
Options forfeited (in shares)	(212,357)
Balance at the end of the period (in shares)	2,374,689		2,786,977
Weighted average exercise price
Balance at the beginning of period (in dollars per share)	$ 7.27
Options granted (in dollars per share)	8.50
Options exercised (in dollars per share)	2.68
Options forfeited (in dollars per share)	11.58
Balance at the end of period (in dollars per share)	$ 7.49		$ 7.27
Additional information
Weighted average remaining contractual term	7 years 4 months 28 days		6 years 3 months 11 days
Stock-based compensation expense	$ 0.7	$ 0.4
Unrecognized compensation costs (in dollars)	$ 4.1
Weighted average period over which unrecognized compensation costs are expected to be recognized	2 years 6 months 7 days
2007 Plan
Stockholders' Equity
Common stock reserved for issuance (in shares)					1,690,448
2014 Plan
Stockholders' Equity
Common stock reserved for issuance (in shares)	707,070			1,027,500
Inducement Plan
Stockholders' Equity
Number of shares awarded	330,000
Number of shares available for future grants	34,000
Grant period of stock awards	10 years
Number of additional years of requisite service period	3 years
Vesting period	1 year
Inducement Plan | On the first anniversary
Stockholders' Equity
Vesting percentage	25.00%
Inducement Plan | Minimum
Stockholders' Equity
Purchase price of awards expressed as a percentage of fair value of shares on the date of grant	100.00%
Percentage of possible payouts of the target award	0.00%
Inducement Plan | Minimum | Individual options
Stockholders' Equity
Vesting percentage	25.00%
Inducement Plan | Maximum
Stockholders' Equity
Percentage of possible payouts of the target award	100.00%
2007 Plan and 2014 Plan | Stock options
Stockholders' Equity
Grant period of stock awards	10 years
2007 Plan and 2014 Plan | Stock options | Minimum
Stockholders' Equity
Purchase price of awards expressed as a percentage of fair value of shares on the date of grant	100.00%
Percentage of voting power owned by shareholder	10.00%
2007 Plan and 2014 Plan | Stock options | Maximum
Stockholders' Equity
Purchase price of awards expressed as a percentage of fair value of shares on the date of grant	110.00%