Discontinued Operations - Additional Information (Detail) - USD ($)			3 Months Ended		9 Months Ended
	Apr. 03, 2017	Jan. 08, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Discontinued operations, amounts directly relate to commercial bussiness					$ 23,000,000
Research and development expense			$ 200,000		200,000
Income tax benefit to continuing operations			(4,798,000)	$ (2,133,000)	(4,798,000)	$ (32,372,000)
Income tax expense to discontinued operations			6,500,000		6,500,000
Baxalta | Asset Sale Agreement [Member] | Development And Commercialization Milestones
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Maximum amount of milestone payments that can be received	$ 33,000,000				33,000,000
Milestone payment received			23,000,000		23,000,000
Income tax benefit to continuing operations			$ (4,800,000)		$ (4,800,000)
January 2017 Corporate Restructuring [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Restructuring activity, announcement date					Jan. 08, 2017
Reduction in headcount, percent		30.00%
January 2017 Corporate Restructuring [Member] | Discontinued Operations [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Restructuring expenses					$ 9,500,000
January 2017 Corporate Restructuring [Member] | Contractual Termination Benefits [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Restructuring expenses				$ 0		$ 9,500,000
January 2017 Corporate Restructuring [Member] | One-time Employee Termination Benefits [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Restructuring activities, description					one-time employee termination benefits are comprised of severance, benefits and related costs, all of which resulted in cash expenditures.