Collaboration and Licensing Agreements - Additional Information (Details) $ in Millions, ¥ in Billions		1 Months Ended					3 Months Ended				9 Months Ended			12 Months Ended
		Oct. 31, 2019 USD ($)	Mar. 31, 2018 CAD ($)	Dec. 31, 2017 USD ($)	Nov. 30, 2017 USD ($)	Jun. 30, 2015 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 JPY (¥)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 USD ($)		Dec. 31, 2017 USD ($)	Jan. 01, 2018 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Current assets							$ 110,834,000					$ 110,834,000		$ 176,371,000	[1]
Current liabilities							17,679,000					17,679,000		17,728,000	[1]
Unbilled license revenue	[1]													5,000,000
Development milestones Received		$ 2,700,000
Revenues							3,013,000			$ 172,000		3,031,000	$ 2,522,000
Cost of revenue							600,000			2,000		600,000	466,000
Withholding tax		$ 300,000
Kyowa Hakko Kirin [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment received					$ 30,000,000							30,000,000
Unbilled license revenue							0					0
Revenues							13,000			200,000		31,000	200,000
Kyowa Hakko Kirin [Member] | Adjustments | ASU 2014-09
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Current assets																	$ 5,000,000
Current liabilities																	$ 1,000,000
Unbilled license revenue							0					0
Uncharged license fees reclassed to accounts payable									$ 1,000,000
Payment of uncharged license fee								$ 1,000,000
Kyowa Hakko Kirin [Member] | Development and Commercialization [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development milestones												55,000,000
Development milestones Received												5,000,000
Commercialization milestones											¥ 8.5	78,500,000
Shanghai Fosun Pharmaceutical Industrial Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment received				$ 12,000,000
Revenues							3,000,000			0		3,000,000	0
Future development milestones																$ 110,000,000
Threshold percentage of net sales for tiered royalties				20.00%
AstraZeneca [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment received						$ 75,000,000
Cost of revenue						10,500,000	600,000	0	1,000,000					500,000		8,400,000
Cost of revenue, Amount Paid						9,900,000	0	$ 1,000,000	$ 0					$ 2,900,000		$ 6,000,000
Remaining balance						$ 65,100,000
AstraZeneca [Member] | Development and Commercialization [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Percentage of royalty revenue (as a percent)						10.00%
Percentage of non royalty revenue (as a percent)						20.00%
AstraZeneca [Member] | Termination Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cost of revenue										0			500,000
Knight | Development and Commercialization [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenues							$ 0			$ 0		0	$ 2,300,000
Total payments, including an up-front payment and development and sales milestones to be received			$ 25									$ 18,900,000

[1] Derived from the audited consolidated financial statements included in the Company’s Annual Report on Form 10K for the year ended December 31, 2018.