Summary of Significant Accounting Policies - Revenue Recognition (Details) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Revenue recognition
Number of types of subscription access revenue contracts offered | item	2
Contract term	1 year
Credits issued related to the Company's direct-to-consumer behavioral health product	$ 0.8	$ 0.4
Credits issued related to the Company's contracts that include client performance guarantees	$ 0.1	$ 0.4	$ 0.4