Collaborative Arrangements (Details) - USD ($)		1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 01, 2012	Jul. 31, 2014	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
GlaxoSmithKline [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from license fees received		$ 6,000,000
Revenue Recognition, Milestone Method, Revenue Recognized						$ 5,000,000
Contingent payment		14,000,000
Milestones receivable		$ 6,500,000
Term of milestone agreement		3 years			24 months
Contingent payment, completion of milestones and agreement						7,500,000
Minimum milestone receivable		$ 5,750,000.00
Maximum milestone receivable		$ 38,500,000.0
License extension acceptance period		3 years
Revenue Recognition, Milestone Method, Termination Notice Period		90 days
License and Services Revenue			$ 500,000		$ 1,000,000		$ 0
Deferred Revenue			4,000,000		4,000,000	5,000,000
Merck [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and Services Revenue			500,000	$ 500,000	1,000,000		$ 1,000,000
Deferred Revenue			$ 1,900,000		$ 1,900,000	$ 900,000
Term of collaborative research and development agreement (years)	5 years