Acquisitions (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011	Mar. 31, 2011	Dec. 31, 2010	Mar. 08, 2012 Stromedix, Inc. [Member]
Summary of purchase price
Cash portion of consideration					$ 75,000,000
Fair value of pre-existing equity ownership					10,200,000
Contingent consideration	(269,900,000)	(151,000,000)	(82,400,000)	(81,200,000)	117,600,000
Total purchase price					$ 202,800,000