Common Stock and Stockholders' Equity (Deficit) - Employee Stock Purchase Plan (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jul. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Stock Purchase Plan
Stock-based compensation		$ 7,723	$ 3,075	$ 533
ESPP
Employee Stock Purchase Plan
Shares reserved for issuance under the plan (in shares)	458,024	458,024
Maximum offering period	27 months
Stock purchase price as a percentage of fair value (as a percent)	85.00%
Stock-based compensation		$ 400	$ 0	$ 0