Income Taxes Unrecognized tax benefits (Details) (USD $)	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized Tax Benefits Beginning Balance	$ 70,490,000	$ 58,125,000	$ 57,140,000
Unrecognized Tax Benefits Increases Related To Acquisitions	45,624,000	0	36,587,000
Unrecognized Tax Benefits, Decreases Resulting from Prior Period Tax Positions	(5,751,000)	(2,153,000)	(49,932,000)
Unrecognized Tax Benefits, Increases Resulting from Current Period Tax Positions	42,328,000	11,992,000	13,951,000
Unrecognized Tax Benefits, Increases Resulting from Prior Period Tax Positions	154,000	2,526,000	379,000
Unrecognized Tax Benefits Ending Balance	152,845,000	70,490,000	58,125,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued [Abstract]
Unrecognized Tax Benefits, Interest on Income Taxes Accrued	3,200,000	3,100,000
Unrecognized Tax Benefits, Income Tax Penalties Accrued	30,600,000	900,000
Unrecognized Tax Benefits, Income Tax Penalties and Interest Expense	$ 800,000	$ 900,000	$ (3,600,000)