Fair Value Measurements (Tables)

12 Months Ended

Mar. 31, 2014

Fair Value, Assets, Liabilities and Stockholders' Equity Measured on Recurring Basis [Abstract]

Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block]

Assets measured at fair value on a recurring basis at March 31, 2014 are as follows (amounts in thousands):

	Quoted Prices in Active Markets for  Identical Instruments (Level 1)		Significant Other Observable Inputs (Level 2)		Significant  Unobservable Inputs (Level 3)		Total Balance
Assets
Money market mutual funds	$	192,159	$	—	$	—	$	192,159
Corporate bonds and debt	—		937,776		6,190		943,966
Government agency bonds	—		681,394		—		681,394
Deposit accounts	—		274,444		—		274,444
Municipal bonds	—		41,709		—		41,709
Auction rate securities	—		—		9,825		9,825
Total assets measured at fair value	$	192,159	$	1,935,323	$	16,015	$	2,143,497

Assets and liabilities measured at fair value on a recurring basis at March 31, 2013 are as follows (amounts in thousands):

	Quoted Prices in Active Markets for Identical Instruments (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total Balance
Assets
Money market mutual funds	$	100,878	$	—	$	—	$	100,878
Marketable equity securities	5,509		—		—		5,509
Corporate bonds and debt	—		678,932		6,190		685,122
Government agency bonds	—		558,153		—		558,153
Deposit accounts	—		427,456		—		427,456
Municipal bonds	—		25,138		—		25,138
Auction rate securities	—		—		33,791		33,791
Total assets measured at fair value	$	106,387	$	1,689,679	$	39,981	$	1,836,047
Liabilities
Contingent consideration	$	—	$	—	$	19,100	$	19,100
Total liabilities measured at fair value	$	—	$	—	$	19,100	$	19,100

Fair Value, Assets and Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Table Text Block]

The following tables present a reconciliation for all assets and liabilities measured at fair value on a recurring basis, excluding accrued interest components, using significant unobservable inputs (Level 3) for the years ended March 31, 2014 and March 31, 2013 (amounts in thousands):

Year ended March 31, 2014	Auction Rate  Securities			Corporate Debt		Contingent Consideration			Total Gains (Losses)
Balance at March 31, 2013	$	33,791		$	6,190	$	(19,100	)	$	—
Total gains (losses) (realized and unrealized):
Included in earnings	1,101			—		(1,370		)	(269		)
Included in other comprehensive income	(332		)	—		—			(332		)
Purchases, sales, issuances, and settlements, net	(24,735		)	—		20,470			—
Balance at March 31, 2014	$	9,825		$	6,190	$	—		$	(601	)

Year ended March 31, 2013	Auction Rate Securities			Corporate Debt		Contingent Consideration			Total Gains (Losses)
Balance at March 31, 2012	$	10,246		$	4,625	$	—		$	—
Total gains (losses) (realized and unrealized):
Included in earnings	(412		)	—		(4,400		)	(4,813		)
Included in other comprehensive income	332			—		—			332
Purchases, sales, issuances, and settlements, net	(650		)	1,565		—			—
Acquisition-related	24,275			—		(14,700		)	—
Balance at March 31, 2013	$	33,791		$	6,190	$	(19,100	)	$	(4,481	)

Fair Value, by Balance Sheet Grouping

Assets measured at fair value on a recurring basis are presented/classified on the consolidated balance sheets at March 31, 2014 as follows (amounts in thousands):

	Quoted Prices  in Active Markets for Identical Instruments (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Total Balance
Assets
Cash and cash equivalents	$	192,159	$	274,444	$	—	$	466,603
Short-term investments	—		878,182		—		878,182
Long-term investments	—		782,697		16,015		798,712
Total assets measured at fair value	$	192,159	$	1,935,323	$	16,015	$	2,143,497

Assets measured at fair value on a recurring basis are presented/classified in the consolidated balance sheets at March 31, 2013 as follows (amounts in thousands):

	Quoted Prices in Active Markets for Identical Instruments (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs  (Level 3)		Total Balance
Assets
Cash and cash equivalents	$	100,878	$	427,456	$	—	$	528,334
Short-term investments	—		1,050,263		—		1,050,263
Long-term investments	5,509		211,960		39,981		257,450
Total assets measured at fair value	$	106,387	$	1,689,679	$	39,981	$	1,836,047