Sale of Commercial Business - Additional Information (Detail)						1 Months Ended	3 Months Ended		9 Months Ended
	Oct. 16, 2017 USD ($)	Apr. 05, 2017 USD ($)	Apr. 03, 2017 USD ($) ft²	Jan. 08, 2017 Employee	May 05, 2011 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 22, 2015
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Aggregate principal amount outstanding redeemed									$ 175,000,000
Dividend date declared									Apr. 05, 2017
Special cash dividend paid		$ 140,000,000
Dividend payable date		May 26, 2017
Dividend payable, date of record		May 17, 2017
Restructuring expenses								$ 809,000		$ 809,000
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
Restructuring and related cost, headcount reduction percentage				30.00%
Restructuring and related cost, number of employees after headcount reduction | Employee				80
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 And Related Activities Description									One-time employee termination benefits are comprised of severance, benefits and related costs, all of which are expected to result in cash expenditures. The majority of these payments were made during the second quarter of 2017. The remaining payments represent severance payments that will be paid over one year.
Severance payments payment period									1 year
2022 Notes [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Interest rate (as a percent)											11.50%
Asset Sale Agreement [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Transition services agreement period			24 months
Special cash dividend paid			$ 140,000,000
Gain from discontinued operations							$ 3,500,000		$ 601,700,000
Asset Sale Agreement [Member] | 2022 Notes [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Aggregate principal amount outstanding redeemed			175,000,000
Additional premium payment			$ 20,100,000
Interest rate (as a percent)			11.50%
Aggregate principal amount of interest redeemed			$ 7,400,000
Ipsen [Member] | Asset Sale Agreement [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Working capital adjustments received						$ 800,000
Ipsen [Member] | Asset Sale Agreement [Member] | Subsequent Event [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Working capital adjustments received	$ 4,900,000
Ipsen [Member] | Asset Sale Agreement [Member] | Manufacturing Facility [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Area of sublease property | ft²			70,237
Lease expiration date			Jun. 30, 2019
Ipsen [Member] | Asset Sale Agreement [Member] | Clinical Trials in Pancreas as First-Line Treatment [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Additional payments receivable on achievement of certain milestone events			$ 225,000,000
Ipsen [Member] | Asset Sale Agreement [Member] | Clinical Trials in Small Cell Lung Cancer [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Additional payments receivable on achievement of certain milestone events			150,000,000
Ipsen [Member] | Asset Sale Agreement [Member] | Other Unrelated Clinical Trials [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Additional payments receivable on achievement of certain milestone events			75,000,000
Ipsen [Member] | Asset Sale Agreement [Member] | Development and Commercialization Milestones [Member]
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
Ipsen [Member] | Asset Sale Agreement [Member] | Sale Milestones in Major European Countries [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Potential milestone payments receivable			18,000,000
Ipsen [Member] | Asset Sale Agreement [Member] | Sale Milestones in Major Non-European and Non-Asian Country [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Potential milestone payments receivable			5,000,000
Ipsen [Member] | Asset Sale Agreement [Member] | Clinical Trials in Lung Cancer [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Potential milestone payments receivable			10,000,000
Ipsen [Member] | Asset Sale Agreement [Member] | Maximum [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Additional payments receivable on achievement of certain milestone events			$ 450,000,000
PharmaEngine [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Upfront license fees paid					$ 10,000,000
PharmaEngine [Member] | Development and Regulatory Milestone [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Maximum milestone payment obligation					80,000,000
PharmaEngine [Member] | Sales Milestone [Member]
Income Statement Balance Sheet And Additional Disclosures By Disposal Groups Including Discontinued Operations [Line Items]
Maximum milestone payment obligation					$ 130,000,000