Share-Based Compensation (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended	38 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012
Share-based compensation expense recognized in the accompanying Consolidated Statements of Operations and Comprehensive Loss
Share-based compensation expense	$ 1,168	$ 338	$ 2,114	$ 397	$ 3,511
Research and development [Member]
Share-based compensation expense recognized in the accompanying Consolidated Statements of Operations and Comprehensive Loss
Share-based compensation expense	592	172	1,032	206	1,693
General and administrative [Member]
Share-based compensation expense recognized in the accompanying Consolidated Statements of Operations and Comprehensive Loss
Share-based compensation expense	$ 576	$ 166	$ 1,082	$ 191	$ 1,818

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6943989&loc=d3e3602-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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