Collaborative Arrangements (Details) - USD ($)	1 Months Ended								3 Months Ended		5 Months Ended	6 Months Ended
	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Apr. 30, 2016	Sep. 30, 2015	Aug. 31, 2015	Jul. 31, 2014	Feb. 29, 2012	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2014	Jun. 30, 2017	Jun. 30, 2016
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenues									$ 10,347,000	$ 16,002,000		$ 18,317,000	$ 23,998,000
Technology Transfer, Collaboration and License Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Termination notice period						30 days
Supply Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred revenue	$ 700,000		$ 700,000						700,000			700,000
Milestone revenue			750,000
Merck [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Sales revenue									3,200,000	1,100,000		5,000,000	2,700,000
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
Maximum milestone receivable						$ 15,000,000
Termination notice period						90 days
License and services revenue									0	600,000		0	1,300,000
Upfront License fee, period for recognition						2 years
Duration of license agreement						3 years
Right of refusal period						5 years
Merck [Member] | Supply Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized	300,000
Termination notice period								24 months
License and services revenue									300,000	300,000		700,000	700,000
Deferred revenue	2,200,000		$ 1,300,000						2,200,000			2,200,000
Upfront License fee, period for recognition								5 years
Term of collaborative research and development agreement								5 years
Optional extension period								5 years
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									0	2,500,000		0	3,000,000
Tate & Lyle [Member] | Research and Development Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Proceeds from license fees received		$ 3,000,000
Revenue recognized									400,000			400,000
Deferred revenue	$ 2,600,000								2,600,000			2,600,000
Term of collaborative research and development agreement		21 months
Licenses revenue									400,000			400,000
Revenues									800,000			800,000
Collaborative Arrangement [Member] | Merck [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License and services revenue									900,000	500,000		1,800,000	700,000
Therapeutic Development Program [Member] | Collaborative Arrangement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue recognized									$ 33,000	$ 400,000		$ 100,000	$ 1,800,000