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Interest rate stated in the contractual debt agreement.

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Significant Accounting Policies (Details 3) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
Significant Accounting Policies (Details 3) (USD $)	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010	Dec. 31, 2010
Consolidation of variable interest entities
Number of variable interest entities in which the entity is not primary beneficiary			8		8
Comprehensive loss:
Unrealized holding losses	$ (290,000)	$ (437,000)	$ (550,000)	$ (286,000)
Reclassification adjustment for realized loss included in net loss				(925,000)
Net loss	(17,889,000)	(25,154,000)	(37,883,000)	(34,811,000)
Comprehensive loss	(18,179,000)	(25,591,000)	(38,433,000)	(36,022,000)
Convertible debt
Interest rate on convertible debt (as a percent)	2.625%		2.625%
Regulus Therapeutics Inc.
Equity method of accounting
Principal plus accrued interest guaranteed on Regulus convertible notes	$ 5,400,000		$ 5,400,000