3. Marketable Securities

The Company’s investments that have original maturities greater than 90 days have been classified as available-for-sale securities in accordance with US GAAP. Marketable securities are categorized on the consolidated balance sheet as restricted investments and marketable securities, as appropriate.

The following table is a summary of available-for-sale securities (in thousands):

As of March 31, 2012:	Amortized Cost	Gross Unrealized Gains	Gross Unrealized Losses	Estimated Fair Value (Net Carrying Amount)
Corporate securities – U.S.................................................	48,011	33	(19)	48,025
U.S. Treasury securities......................................................	30,264	1	(4)	30,261
Agency discount notes.......................................................	16,789	8	(1)	16,796
Commercial paper..............................................................	23,719	5	(15)	23,709
Total securities.................................................................	$ 118,783	$ 47	$ (39)	$ 118,791

The Company’s specifically identified gross unrealized losses of $39 thousand relates to 37 different securities with a total amortized cost of approximately $72.6 million at March 31, 2012. Because the Company does not intend to sell the investments at a loss and the Company will not be required to sell the investments before recovery of its amortized cost basis, it did not consider the investment in these securities to be other-than-temporarily impaired at March 31, 2012. Further, the securities with gross unrealized losses had been in a continuous unrealized loss position for less than 12 months as of March 31, 2012.

As of March 26, 2011:	Amortized Cost	Gross Unrealized Gains	Gross Unrealized Losses	Estimated Fair Value (Net Carrying Amount)
Corporate securities – U.S.................................................	64,228	22	(38)	64,212
U.S. Treasury securities......................................................	35,268	13	—	35,281
Agency discount notes.......................................................	16,588	5	(2)	16,591
Commercial paper..............................................................	56,130	23	(7)	56,146
Total securities.................................................................	$ 172,214	$ 63	$ (47)	$ 172,230

The Company’s specifically identified gross unrealized losses of $47 thousand relates to 28 different securities with a total amortized cost of approximately $61.8 million at March 26, 2011. Because the Company does not intend to sell the investments at a loss and the Company will not be required to sell the investments before recovery of its amortized cost basis, it did not consider the investment in these securities to be other-than-temporarily impaired at March 26, 2011. Further, the securities with gross unrealized losses had been in a continuous unrealized loss position for less than 12 months as of March 26, 2011.

The cost and estimated fair value of available-for-sale investments by contractual maturity were as follows:


	March 31, 2012		March 26, 2011
	Amortized Cost	Estimated Fair Value	Amortized Cost	Estimated Fair Value
Within 1 year.......................................................................	$ 115,871	$ 115,876	$ 159,516	$ 159,528
After 1 year.........................................................................	2,912	2,915	12,698	12,702
	$ 118,783	$ 118,791	$ 172,214	$ 172,230