Organization and Basis of Presentation Narrative (Details) (USD $) In Millions, unless otherwise specified	Mar. 27, 2013
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Common stock value authorized for controlled sale	$ 25.0

Common stock value authorized for sale in an “at-the-market” offering as defined in Rule 415 of the Securities Act of 1933, as amended.

No definition available.

Name:	zgnx_CommonStockValueAuthorized
Namespace Prefix:	zgnx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant