4. 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, 2011, January 31, 2011 and April 30, 2010 were as follows:


	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
Federal government agencies		55,122		205		—			55,327
Auction rate securities		30,150		—		(3,434	)		26,716
Treasury bills		19,661		92		—			19,753
Variable rate demand notes		1,900		—		—			1,900

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

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

As of January 31, 2011
Short-term Investments:
Municipal and pre-refunded municipal bonds	$	42,996	$	48	$	(9	)	$	43,035
Federal government agencies		40,842		80		—			40,922
Treasury bills		7,004		4		—			7,008
Variable rate demand notes		1,900		—		—			1,900
FDIC insured corporate bonds		23,489		66		—			23,555

		116,231		198		(9	)		116,420

Long-term Investments:
Corporate bonds		137,540		173		(154	)		137,559
Municipal and pre-refunded municipal bonds		143,711		216		(558	)		143,369
Federal government agencies		18,225		30		(2	)		18,253
Auction rate securities		33,250		—		(3,788	)		29,462
Treasury bills		23,311		34		—			23,345

		356,037		453		(4,502	)		351,988

	$	472,268	$	651	$	(4,511	)	$	468,408

As of April 30, 2010
Short-term Investments:
Municipal and pre-refunded municipal bonds	$	111,075	$	178	$	(24	)	$	111,229
Federal government agencies		127,336		212		(15	)		127,533
Treasury bills		49,711		26		—			49,737
FDIC insured corporate bonds		35,211		200		—			35,411

		323,333		616		(39	)		323,910

Long-term Investments:
Municipal and pre-refunded municipal bonds		40,163		234		(46	)		40,351
Federal government agencies		99,828		201		(45	)		99,984
Auction rate securities		37,625		—		(4,120	)		33,505
FDIC insured corporate bonds		15,537		90		—			15,627

		193,153		525		(4,211	)		189,467

	$	516,486	$	1,141	$	(4,250	)	$	513,377

Proceeds from the sale and maturities of available-for-sale securities were $115,442 and $116,392 for the three months ended April 30, 2011 and 2010, respectively. The Company included in other income net realized gains of $28 and net realized losses of $100 for the three months ended April 30, 2011 and April 30, 2010, respectively. Amortization of discounts and premiums, net, resulted in charges of $2,322 and $2,237 for the three months ended April 30, 2011 and April 30, 2010, respectively.

As of April 30, 2011, the par value of the Company's auction rate securities ("ARS") was $30,150 and the estimated fair value was $26,716. The Company's ARS portfolio consists of "A" or better rated ARS that represent interests in municipal and student loan related collateralized debt obligations, all of which are guaranteed by either government agencies and/or insured by private insurance agencies at 97% or greater of par value. 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 full 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.