Intangible assets and license agreements (Details) (USD $)	12 Months Ended												12 Months Ended		12 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010	Mar. 31, 2011 Trans Tech Pharma Inc License Agreement [Member]	Mar. 31, 2011 Gruenenthal Group Agreement [Member]	Feb. 28, 2011 Nycomed License Agreement [Member]	Mar. 31, 2010 Nycomed License Agreement [Member]	Mar. 31, 2010 AstraZeneca License Agreement [Member]	Mar. 31, 2010 AstraZeneca UK License Agreement [Member]	Mar. 31, 2010 Almirall License Agreement [Member]	Oct. 31, 2010 Takeda Pharmaceutical Company [Member]	Mar. 31, 2012 Blue Ash [Member]	Mar. 31, 2012 Licensing Agreements [Member]	Mar. 31, 2011 Licensing Agreements [Member]	Mar. 31, 2012 Product Rights [Member]	Mar. 31, 2011 Product Rights [Member]	Mar. 31, 2012 Buy-out of royalty agreements [Member]	Mar. 31, 2011 Buy-out of royalty agreements [Member]	Mar. 31, 2012 Trade Names [Member]	Mar. 31, 2011 Trade Names [Member]
Amortized intangible assets:
Weighted average amortization period	13												11		11		10
Gross carrying amount	$ 2,326,738,000	$ 900,424,000											$ 1,403,114,000	$ 434,446,000	$ 90,817,000	$ 61,788,000	$ 798,617,000	$ 370,000,000	$ 34,190,000	$ 34,190,000
Accumulated amortization	222,690,000	174,930,000											107,314,000	94,619,000	52,929,000	42,672,000	28,257,000	4,582,000	34,190,000	33,057,000
Finite-Lived Intangible Assets, Future Amortization Expense [Abstract]
Expected amortization expense, year ending March 31, 2013	104,077,000
Expected amortization expense, year ending March 31, 2014	143,759,000
Expected amortization expense, year ending March 31, 2015	171,871,000
Expected amortization expense, year ending March 31, 2016	190,790,000
Expected amortization expense, year ending March 31, 2017	214,071,000
Future expected amortization expense	824,568,000
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Amortization expense	80,900,000	30,800,000	31,400,000
Acquired Finite-lived Intangible Asset, Amount		1,000,000,000
Intangible Assets recorded as per agreement	429,000,000
Amount of royalty buyout	357,000,000
Upfront license agreement payment				50,000,000	66,100,000		100,000,000		229,000,000	75,000,000		40,000,000
Number of license agreements		3	4
Payment obligation under the terms of the asset purchase agreement					100,000,000
Upfront receipt of license/collaboration agreement payment								40,000,000
License/collaboration agreement development milestone payment						$ 182,000,000					$ 8,000,000