Stock-Based Employee Compensation Plans - Summary of Status of Unvested Options Outstanding and Changes in Number of Shares Subject to and in Weighted Average Grant Date Fair Values (Details) - $ / shares	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Number of Shares Subject to Options
Unvested, Beginning of Period (in shares)	215,926	468,504
Granted (in shares)	379,551	112,828
Vested (in shares)	(52,738)	(74,301)
Forfeited/Canceled (in shares)	(42,057)	(27,214)
Unvested, End of Period (in shares)	500,682	479,817
Weighted Average Grant Date Fair Value
Unvested, Beginning of Period (in dollars per share)	$ 2.93	$ 2.68
Granted (in dollars per share)	2.76	3.13
Vested (in dollars per share)	2.93	2.57
Forfeited/Canceled (in dollars per share)	2.90	2.26
Unvested, End of Period (in dollars per share)	$ 2.80	$ 2.86