Stockholders' Equity - ESPP (Details) - Employee Stock Purchase Plan - $ / shares	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015	Jan. 01, 2016
Employee Stock Purchase Plan (Abstract)
Shares available for issuance under ESPP	867,089	867,089		911,725
Number of shares purchased under ESPP	0	44,636	74,805
Average purchase price of shares under ESPP	$ 3.09	$ 3.09	$ 4.08