Fair Value Measurement (Liabilities Narrative) (Details 3) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Fair Value Measurement Liabilities Narrative Details 3
Brigham Women's Hospital royalty liability, fair value	$ 4.3	$ 4.9
Brigham Women's Hospital royalty liability, carrying value	$ 6.6	$ 7.6

Carrying value as of the balance sheet date of obligations incurred through that date and payable for royalties.

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