Fair Value of Financial Assets and Liabilities - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Assets:
Marketable securities	$ 3,000	$ 35,209
Recurring Basis
Assets:
Total assets at fair value	65,758	64,937
Recurring Basis | United States Treasury Notes
Assets:
Marketable securities	3,000	35,209
Money Market Funds | Recurring Basis
Assets:
Cash equivalents	62,758	20,734
Agency bonds | Recurring Basis
Assets:
Cash equivalents		8,994
Level 2 | Recurring Basis
Assets:
Total assets at fair value	65,758	64,937
Level 2 | Recurring Basis | United States Treasury Notes
Assets:
Marketable securities	3,000	35,209
Level 2 | Money Market Funds | Recurring Basis
Assets:
Cash equivalents	$ 62,758	20,734
Level 2 | Agency bonds | Recurring Basis
Assets:
Cash equivalents		$ 8,994