Fair Value Measurement (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets fair value	$ 73,390	$ 73,220
Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets fair value	15,633	15,003
Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets fair value	57,757	58,217
Money Market Funds
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets fair value	15,633	15,003
Money Market Funds | Level 1
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets fair value	15,633	15,003
Corporate debt securities
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets fair value	6,620	10,738
Corporate debt securities | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets fair value	6,620	10,738
Commercial paper
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets fair value	51,137	47,479
Commercial paper | Level 2
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Assets fair value	$ 51,137	$ 47,479