Consolidated Statements of Comprehensive Loss (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Non-cash stock-based compensation expenses included in operating expenses are as follows:
Research and development	$ 14,369	$ 8,041	$ 10,921
General and administrative	$ 6,334	$ 4,319	$ 5,755

The aggregate amount of noncash, equity-based employee and non-employee remuneration classified as general and administrative expenses.

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration