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Common Stock Subject to Conditional Redemption - Pfizer Settlement Agreement (Details) (USD $)
In Millions, except Share data, unless otherwise specified
1 Months Ended
Apr. 30, 1996
Mar. 31, 2012
Dec. 31, 2011
compound
Common Stock Subject to Conditional Redemption - Pfizer Settlement Agreement (Textual) [Abstract]      
Date of settlement agreement April 1996    
Exchange ratio of common shares $ 74.25    
Number of compounds covered in settlement agreement     2
Common stock redeemed     112,371
Reclassification to permanent equity   $ 8.3