Fair Value Measurements (Details) - Recurring basis - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Money market funds
Assets
Cash and cash equivalents, fair value	$ 21,699	$ 25,629
Certificates of deposit
Assets
Investments	2,184	3,922
Level 1 | Money market funds
Assets
Cash and cash equivalents, fair value	21,699	25,629
Level 1 | Certificates of deposit
Assets
Investments	$ 2,184	$ 3,922