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Significant Accounting Policies - Additional Information (Detail)	9 Months Ended		12 Months Ended
	Sep. 30, 2018 USD ($) Segment	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Jan. 01, 2018 USD ($)	Jan. 20, 2017 USD ($)	Dec. 31, 2012 USD ($)
Significant Accounting Policies [Line Items]
Trade receivables, credit period	30 days
U.S. federal corporate tax rate	21.00%		34.00%
Number of operating segments | Segment	1
Accumulated deficit	$ (1,354,863,000)		$ (1,271,869,000)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Accumulated deficit				$ 200,000
Minimum
Significant Accounting Policies [Line Items]
Trade receivables, credit period	30 days
Maximum
Significant Accounting Policies [Line Items]
Trade receivables, credit period	60 days
Embedded Derivative Financial Instruments | BioPharma Debt
Significant Accounting Policies [Line Items]
Maximum repayment of future revenue and receivables						$ 150,000,000
Fair value of embedded derivative liability	$ 0	$ 0
Gain (loss) on change in fair value of derivative liabilities	$ 0	$ 0
Embedded Derivative Financial Instruments | BioPharma Debt | Minimum
Significant Accounting Policies [Line Items]
Derivative liability fair value assumption, coupon rate	5.40%	5.80%
Derivative liability fair value assumptions, market yields	7.00%	10.20%
Embedded Derivative Financial Instruments | BioPharma Debt | Maximum
Significant Accounting Policies [Line Items]
Derivative liability fair value assumption, coupon rate	10.80%	10.80%
Derivative liability fair value assumptions, market yields	12.00%	18.40%
Embedded Derivative Financial Instruments | BioPharma Debt | Measurement Input, Expected Term | Minimum
Significant Accounting Policies [Line Items]
Derivative liability fair value assumptions, term	1 year 6 months	2 years 3 months 18 days
Embedded Derivative Financial Instruments | BioPharma Debt | Measurement Input, Expected Term | Maximum
Significant Accounting Policies [Line Items]
Derivative liability fair value assumptions, term	4 years 3 months 18 days	4 years 3 months 18 days
Customer A | Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	26.00%	28.00%
Customer A | Accounts Receivable | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	37.00%	36.00%
Customer B | Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	31.00%	27.00%
Customer B | Accounts Receivable | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	33.00%	27.00%
Customer C | Gross Product Sales | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	31.00%	35.00%
Customer C | Accounts Receivable | Customer Concentration Risk
Significant Accounting Policies [Line Items]
Concentration risk percentage	17.00%	24.00%
2017 Notes
Significant Accounting Policies [Line Items]
Aggregate principal amount of notes	$ 30,000,000
Convertible senior notes, discount	1,200,000
Convertible Debt | 2017 Notes
Significant Accounting Policies [Line Items]
Convertible senior notes, discount	$ 800,000		$ 1,000,000		$ 1,200,000

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