Collaboration and Licensing Agreements - Additional Information (Detail) $ in Millions, ¥ in Billions	1 Months Ended				3 Months Ended	6 Months Ended			12 Months Ended
	Dec. 31, 2017 USD ($)		Nov. 30, 2017 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2018 CAD ($)	Jun. 30, 2018 JPY (¥)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)		Jan. 02, 2018 USD ($)
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Current assets	$ 149,712,000	[1]			$ 221,688,000			$ 221,688,000	$ 149,712,000	[1]	$ 5,000,000
Current liabilities	17,871,000	[1]			15,609,000			15,609,000	17,871,000	[1]	1,000,000
Revenue					30,000			2,350,000
Cost of revenue								464,000
Other
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue					30,000			30,000
Adjustments | ASU 2014-09
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Current assets					5,000,000			5,000,000			5,000,000
Current liabilities					1,000,000			1,000,000			1,000,000
Kyowa Hakko Kirin [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment received			$ 30,000,000
Kyowa Hakko Kirin [Member] | Product supply
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue					30,000			30,000
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
Shanghai Fosun Pharmaceutical Industrial Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment received	12,000,000
Revenue					0			0
Future development milestones	$ 113,000,000
Threshold percentage of net sales for tiered royalties	20.00%
Astra Zeneca [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront payment received				$ 75,000,000
Development And Commercialization [Member] | Kyowa Hakko Kirin [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Development milestones								55,000,000
Commercialization milestones | ¥							¥ 8.5
Development And Commercialization [Member] | Shanghai Fosun Pharmaceutical Industrial Development [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cost of revenue									2,400,000
Development And Commercialization [Member] | Astra Zeneca [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cost of revenue								1,000,000
Development And Commercialization [Member] | Knight Therapeutics Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revenue					$ 0			2,300,000
Total payments, including an up-front payment and development and sales milestones to be received						$ 25
Cost of revenue								500,000	$ 6,000,000
Termination Agreement [Member] | Astra Zeneca [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cost of revenue								$ 500,000
Termination Agreement [Member] | Knight Therapeutics Inc [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cost of revenue				$ 9,900,000

[1] Derived from the audited consolidated financial statements included in the Company’s Annual Report on Form 10K for the year ended December 31, 2017.