Fair Value Measurements (Details) (USD $)	6 Months Ended
	Jun. 30, 2014 item	Jun. 06, 2014	Dec. 31, 2013
Assets
Cash and Cash equivalents:	$ 48,371,000
Liabilities
Warrant liability			1,945,000
Number of work statements executed with the Nordic Work Statements	3
Conversion of right to receive shares of Series A-6 to the right to receive total potential cash payments upon completion of IPO		4,300,000
Cash
Assets
Cash and Cash equivalents:	1,133,000		2,710,000
Money market funds
Assets
Cash and Cash equivalents:	31,417,000		9,593,000
Domestic corporate debt securities
Assets
Cash and Cash equivalents:	5,381,000
Domestic corporate commercial paper
Assets
Cash and Cash equivalents:	10,440,000
Recurring basis | Level 1
Assets
Cash and Cash equivalents:	32,550,000		12,303,000
Recurring basis | Level 1 | Cash
Assets
Cash and Cash equivalents:	1,133,000		2,710,000
Recurring basis | Level 1 | Money market funds
Assets
Cash and Cash equivalents:	31,417,000		9,593,000
Recurring basis | Level 2
Assets
Cash and Cash equivalents:	15,821,000
Marketable securities	30,650,000
Recurring basis | Level 2 | Domestic corporate debt securities
Assets
Cash and Cash equivalents:	5,381,000
Marketable securities	22,152,000
Recurring basis | Level 2 | Domestic corporate commercial paper
Assets
Cash and Cash equivalents:	10,440,000
Marketable securities	8,498,000
Recurring basis | Level 3
Liabilities
Warrant liability			1,945,000
Stock liability			5,328,000
Total liabilities carried at fair value			7,273,000
Recurring basis | Estimated Fair Value
Assets
Cash and Cash equivalents:	48,371,000		12,303,000
Marketable securities	30,650,000
Liabilities
Warrant liability			1,945,000
Stock liability			5,328,000
Total liabilities carried at fair value			7,273,000
Recurring basis | Estimated Fair Value | Cash
Assets
Cash and Cash equivalents:	1,133,000		2,710,000
Recurring basis | Estimated Fair Value | Money market funds
Assets
Cash and Cash equivalents:	31,417,000		9,593,000
Recurring basis | Estimated Fair Value | Domestic corporate debt securities
Assets
Cash and Cash equivalents:	5,381,000
Recurring basis | Estimated Fair Value | Domestic corporate commercial paper
Assets
Cash and Cash equivalents:	10,440,000
Recurring basis | Estimated Fair Value | Domestic corporate debt securities
Assets
Marketable securities	22,152,000
Recurring basis | Estimated Fair Value | Domestic corporate commercial paper
Assets
Marketable securities	$ 8,498,000