Fair Value Measurements (Reconciliation Of Changes In Fair Value Of Level 3 Financial Assets) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Mar. 31, 2010
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Payments	$ (846)	$ 0	$ 0
Auction Rate Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	17,482	28,475
Additions to Level 3	0
Transfers out of Level 3	(17,612)	(4,007)
Change in fair value (included within research and development expense)	0
ARSs redeemed by issuers at par	(500)	(8,600)
Unrealized gains (loss) included in accumulated other comprehensive income (loss)	2,112	1,622
Unrealized gain (loss) included in earnings	(21)	(8)
Payments	0
Balance at end of period	1,461	17,482
Contingent Purchase Consideration [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	0
Additions to Level 3	8,000
Change in fair value (included within research and development expense)	1,059
ARSs redeemed by issuers at par	0
Unrealized gains (loss) included in accumulated other comprehensive income (loss)	0
Unrealized gain (loss) included in earnings	0
Payments	(846)
Balance at end of period	8,213
Contingent Contractual Non-Compliance Liability [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance at beginning of period	0
Additions to Level 3	1,600
Change in fair value (included within research and development expense)	(900)
ARSs redeemed by issuers at par	0
Unrealized gains (loss) included in accumulated other comprehensive income (loss)	0
Unrealized gain (loss) included in earnings	0
Payments	0
Balance at end of period	$ 700