Investments (Tables)

6 Months Ended

Sep. 30, 2012

Investments, Debt and Equity Securities [Abstract]

Available-for-sale investments at September 30, 2012 were as follows:



(in thousands)	Cost			Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. government treasuries and agencies securities	$	145,816		$	19	$	—		$	145,835
Money market funds	62,100								62,100
Corporate bonds	13,678			18		—			13,696
International government bonds	4,606					(1		)	4,605
Corporate commercial paper	1,000								1,000
Bank deposits	11,183								11,183
Total available-for-sale investments	238,383			37		(1		)	238,419
Less amounts classified as cash equivalents	(67,497		)	—		—			(67,497		)
Short-term investments	$	170,886		$	37	$	(1	)	$	170,922

Available-for-sale investments at April 1, 2012 were as follows:



(in thousands)	Cost			Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. government treasuries and agencies securities	$	156,331		$	8	$	(24	)	$	156,315
Money market funds	104,596			—		—			104,596
Corporate bonds	21,485			59		(6		)	21,538
International government bonds	4,650			1		(3		)	4,648
Corporate commercial paper	3,148			—		—			3,148
Bank deposits	11,633			—		—			11,633
Municipal bonds	652			1					653
Total available-for-sale investments	302,495			69		(33		)	302,531
Less amounts classified as cash equivalents	(111,996		)	—		—			(111,996		)
Short-term investments	$	190,499		$	69	$	(33	)	$	190,535

Contractual Maturity of Available-For-Sale Debt Securities

The cost and estimated fair value of available-for-sale securities at September 30, 2012, by contractual maturity, were as follows:



(in thousands)	Amortized Cost		Estimated Fair Value
Due in 1 year or less	$	237,732	$	237,769
Due in 1-2 years	650		650
Total investments in available-for-sale securities	$	238,382	$	238,419

Gross Unrealized Losses and Fair Value of Investments in Continuous Loss Position

The following table shows the gross unrealized losses and fair value of the Company’s investments with unrealized losses as of September 30, 2012, aggregated by length of time that individual securities have been in a continuous loss position.



	Less Than 12 Months					12 Months or Greater				Total
(in thousands)	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Corporate bonds	$	552	$	(1	)	$	—	$	—	$	552	$	(1	)
U.S. government treasuries and agencies securities	1,350		—			—		—		1,350		—
International government bonds	4,606		—			—		—		4,606		—
Total	$	6,508	$	(1	)	$	—	$	—	$	6,508	$	(1	)

The following table shows the gross unrealized losses and fair value of the Company’s investments with unrealized losses, as of April 1, 2012, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position.



	Less Than 12 Months					12 Months or Greater				Total
(in thousands)	Fair Value		Unrealized Loss			Fair Value		Unrealized Loss		Fair Value		Unrealized Loss
Corporate bonds	$	4,213	$	(7	)	$	—	$	—	$	4,213	$	(7	)
U.S. government treasuries and agencies securities	114,056		(24		)	—		—		114,056		(24		)
International government bonds	2,550		(2		)	—		—		2,550		(2		)
Total	$	120,819	$	(33	)	$	—	$	—	$	120,819	$	(33	)