Exercise price of the warrants.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Article 12

-Section 13

-Sentence Column A

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- Definition

The number of warrants issued in exchange for the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

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- Definition

The cash inflow associated with the amount received from holders exercising their stock warrants.

+ References

No definition available.

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- Definition

Number of non-option equity instruments exercised by participants.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iv)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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- Definition

Aggregate number of shares of common stock obtainable through exercise of warrants.

+ References

No definition available.

+ Details

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- Definition

Common Stock Warrant Exercise Price Per Share

+ References

No definition available.

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- Definition

Fair value of warrant liabilities as of the balance sheet date.

+ References

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- Definition

Term over which common stock warrants are exercisable, from date of issuance.

+ References

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Common Stock Warrants - Additional Informational (Detail) (USD $)	0 Months Ended	1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 27, 2012	Jul. 31, 2011	Mar. 31, 2015	Dec. 31, 2014
Schedule Of Common Stock [Line Items]
Shares of common stock exercisable through warrants	15,784,200
Warrants exercise price per share	$ 2.50
Term of common stock warrant exercisable (years)	5 years	10 years
Proceeds from warrant exercises			$ 0us-gaap_ProceedsFromWarrantExercises	$ 1,163,000us-gaap_ProceedsFromWarrantExercises
Fair value of warrant liabilities			4,585,000zgnx_FairValueOfWarrantsLiabilities	4,978,000zgnx_FairValueOfWarrantsLiabilities
Warrant exercisable to Healthcare Royalty, shares		225,000
Warrant exercisable to Healthcare Royalty, price per share (usd per share)		$ 9.00invest_InvestmentWarrantsExercisePrice
Healthcare Royalty
Schedule Of Common Stock [Line Items]
Fair value of warrant liabilities			$ 98,000	$ 115,000
Common stock warrants
Schedule Of Common Stock [Line Items]
Warrants exercised				465,250