Number of Warrants Outstanding (Detail)	Jun. 30, 2013	Dec. 31, 2012
Class of Warrant or Right [Line Items]
Classified warrants	10,441,431	11,197,454
Liabilities
Class of Warrant or Right [Line Items]
Classified warrants	8,050,709	8,050,709
Equity
Class of Warrant or Right [Line Items]
Classified warrants	2,390,722	3,146,745

Number of warrants or rights outstanding.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(i))

-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph i

-Article 4

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant