3. Marketable Securities

During all periods presented, marketable securities are classified as available-for-sale. The amortized cost, gross unrealized gains (losses) and fair value of available-for-sale securities by major security type and class of security as of April 30, 2012, January 31, 2012 and April 30, 2011 were as follows:


	Amortized Cost		Unrealized Gains		Unrealized (Losses)			Fair Value
As of April 30, 2012
Short-term Investments:
Corporate bonds	$	40,934	$	23	$	(14	)	$	40,943
Municipal and pre-refunded municipal bonds		36,465		96		(5	)		36,556
Treasury bills		11,694		—		(1	)		11,693
Certificate of deposit		13,665		4		—			13,669
Commercial paper		7,572		9		—			7,581
Federal government agencies		6,615		—		(1	)		6,614

		116,945		132		(21	)		117,056

Long-term Investments:
Corporate bonds		46,685		148		(26	)		46,807
Municipal and pre-refunded municipal bonds		18,809		169		(5	)		18,973
Treasury bills		12,944		6		—			12,950
Certificate of deposit		8,170		2		(1	)		8,171
Auction rate securities		4,925		—		(595	)		4,330

		91,533		325		(627	)		91,231

	$	208,478	$	457	$	(648	)	$	208,287


As of January 31, 2012
Short-term Investments:
Corporate bonds	$	34,899	$	7	$	(28	)	$	34,878
Municipal and pre-refunded municipal bonds		41,519		135		(10	)		41,644
Certificate of deposit		5,225		—		—			5,225
Commercial paper		3,580		12		—			3,592
Federal government agencies		4,513		2		—			4,515

		89,736		156		(38	)		89,854

Long-term Investments:
Corporate bonds		60,852		277		(72	)		61,057
Municipal and pre-refunded municipal bonds		18,410		186		(6	)		18,590
Treasury bills		14,982		6		—			14,988
Certificate of deposit		6,970		—		(1	)		6,969
Federal government agencies		5,111		2		(1	)		5,112
Auction rate securities		22,975		—		(2,778	)		20,197

		129,300		471		(2,858	)		126,913

	$	219,036	$	627	$	(2,896	)	$	216,767


	Amortized Cost		Unrealized Gains		Unrealized (Losses)			Fair Value
As of April 30, 2011
Short-term Investments:
Corporate bonds	$	5,377	$	18	$	—		$	5,395
Municipal and pre-refunded municipal bonds		36,498		24		(30	)		36,492
Federal government agencies		16,284		17		—			16,301
FDIC insured corporate bonds		10,478		22		—			10,500

		68,637		81		(30	)		68,688

Long-term Investments:
Corporate bonds		132,937		513		(46	)		133,404
Municipal and pre-refunded municipal bonds		96,748		367		(269	)		96,846
Treasury bills		19,661		92		—			19,753
Federal government agencies		55,122		205		—			55,327
Auction rate securities		30,150		—		(3,434	)		26,716
Variable rate demand notes		1,900		—		—			1,900

		336,518		1,177		(3,749	)		333,946

	$	405,155	$	1,258	$	(3,779	)	$	402,634

Proceeds from the sale and maturities of available-for-sale securities were $53,829 and $115,442 for the three months ended April 30, 2012 and 2011, respectively. The Company included in Other income, net, in the Condensed Consolidated Statement of Income, realized gains of $127 and $28 and a net charge related to amortization of discounts and premiums of $1,235 and $2,322 for the three months ended April 30, 2012 and April 30, 2011, respectively.

As of April 30, 2012, the par value of the Company's Auction Rate Securities ("ARS") was $4,925 and the estimated fair value was $4,330. The Company's ARS portfolio consists of "A" or better rated ARS that represent interests in municipal obligations. To date, the Company has collected all interest payable on outstanding ARS when due and have not been informed by the issuers that accrued interest payments are currently at risk. The Company does not have the intent to sell the underlying securities prior to their recovery and the Company believes it is not likely that it will be required to sell the underlying securities prior to their anticipated recovery of full amortized cost.