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Fair Value Measurements - Acquisition of CyDex (Details) - Cydex Pharmaceuticals, Inc - Contingent Consideration Classified as Equity	6 Months Ended	12 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Credit Derivatives [Line Items]
Average probability of commercialization (as a percent)	12.50%	12.50%
Market price of risk	0.029	0.029
Measurement Input, Price Volatility
Credit Derivatives [Line Items]
Revenue volatility (as a percent)	0.25	0.25

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Average Probability of Commercialization

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Fair Value Inputs, Sales Beta

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Value of input used to measure investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258

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