Acquisitions and Collaborations (Collaborations) (Details) (USD $) In Millions, unless otherwise specified		3 Months Ended		3 Months Ended		3 Months Ended			3 Months Ended	12 Months Ended		3 Months Ended	12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012 Collaborative Arrangement II with Molecular Partners [Member]	Dec. 31, 2012 Collaborative Arrangement II with Molecular Partners [Member]	Jun. 30, 2011 Collaborative Arrangement I With Molecular Partners [Member]	Dec. 31, 2012 Collaborative Arrangement I With Molecular Partners [Member]	Sep. 30, 2011 Collaborative Arrangement With MAP [Member]	Mar. 31, 2011 Collaborative Arrangement With MAP [Member]	Dec. 31, 2012 Collaborative Arrangement With MAP [Member]	Mar. 31, 2010 Collaborative Arrangement With Serenity [Member]	Dec. 31, 2010 Collaborative Arrangement With Serenity [Member]	Dec. 31, 2012 Collaborative Arrangement With Serenity [Member]	Mar. 31, 2010 Collaborative Arrangement With Bristol Myers Squibb [Member]	Dec. 31, 2010 Collaborative Arrangement With Bristol Myers Squibb [Member]
Business Collaborations [Line Items]
Date of collaboration agreement		Aug. 21, 2012		May 04, 2011			Jan. 28, 2011		Mar. 31, 2010			Mar. 31, 2010
Upfront payment		$ 62.5		$ 45.0			$ 60.0			$ 43.0
Potential future milestone payments			1,400.0		375.0			97.0
Share of the cost of additional development activities (in hundredths)											50.00%
Milestone payment						20.0
Net upfront payment received													36.0
Potential future milestone receipts	$ 86.0