Collaborative Arrangements (Details) - USD ($)	1 Months Ended					3 Months Ended		5 Months Ended	6 Months Ended
	Apr. 30, 2016	Sep. 30, 2015	Aug. 31, 2015	Jul. 31, 2014	Feb. 29, 2012	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Technology Transfer, Collaboration and License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Termination notice period			30 days
GlaxoSmithKline [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from license fees received				$ 6,000,000
Revenue recognized	$ 7,500,000	$ 6,500,000						$ 5,000,000
Minimum milestone receivable				5,750,000.00
Maximum milestone receivable				$ 38,500,000.0
Termination notice period				90 days
Term of milestone agreement				3 years
License and services revenue						$ 2,500,000	$ 500,000		$ 3,000,000	$ 1,000,000
Deferred revenue						0			0		$ 3,000,000
Merck [Member] | Technology Transfer, Collaboration and License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from license fees received			$ 5,000,000
Revenue recognized		$ 5,000,000
Termination notice period			90 days
License and services revenue						600,000			1,300,000
Deferred revenue						2,700,000			2,700,000		4,000,000
Upfront License fee, period for recognition			2 years
Contingent payment, completion of milestones and agreement			$ 8,000,000
Potential royalty revenue			$ 15,000,000
Duration of license agreement			3 years
Right of refusal period			5 years
Contingent termination revenue			$ 8,000,000
Merck [Member] | Supply Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and services revenue						300,000	$ 500,000		700,000	$ 1,000,000
Deferred revenue						$ 2,000,000			$ 2,000,000		$ 1,000,000
Upfront License fee, period for recognition					5 years
Term of collaborative research and development agreement (years)					5 years
Optional extension period					5 years
Merck [Member] | Minimum [Member] | Technology Transfer, Collaboration and License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Duration of technology transfer			15 months
Merck [Member] | Maximum [Member] | Technology Transfer, Collaboration and License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Duration of technology transfer			24 months