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 July 31, 2012, January 31, 2012 and July 31, 2011 were as follows:


	Amortized Cost		Unrealized Gains		Unrealized (Losses)			Fair Value
As of July 31, 2012
Short-term Investments:
Corporate bonds	$	53,713	$	71	$	(8	)	$	53,776
Municipal and pre-refunded municipal bonds		28,019		95		(7	)		28,107
Treasury bills		21,425		5		—			21,430
Certificate of deposit		20,671		13		(2	)		20,682
Commercial paper		7,279		8		—			7,287
Federal government agencies		4,608		—		—			4,608

		135,715		192		(17	)		135,890

Long-term Investments:
Corporate bonds		47,905		150		(18	)		48,037
Municipal and pre-refunded municipal bonds		24,646		78		(23	)		24,701
Treasury bills		8,855		10		—			8,865
Certificate of deposit		4,514		2		—			4,516
Auction rate securities		4,925		—		(595	)		4,330
Federal government agencies		1,213		2		—			1,215

		92,058		242		(636	)		91,664

	$	227,773	$	434	$	(653	)	$	227,554


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
Auction rate securities		22,975		—		(2,778	)		20,197
Federal government agencies		5,111		2		(1	)		5,112

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

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

As of July 31, 2011
Short-term Investments:
Corporate bonds	$	10,062	$	22	$	(6	)	$	10,078
Municipal and pre-refunded municipal bonds		38,079		57		(17	)		38,119
Federal government agencies		7,130		16		—			7,146
FDIC insured corporate bonds		4,000		4		—			4,004

		59,271		99		(23	)		59,347

Long-term Investments:
Corporate bonds		134,199		857		(13	)		135,043
Municipal and pre-refunded municipal bonds		85,639		624		(39	)		86,224
Treasury bills		19,639		190		—			19,829
Certificate of deposit		5,144		—		(1	)		5,143
Auction rate securities		26,525		—		(3,021	)		23,504
Federal government agencies		49,872		386		—			50,258
Variable rate demand notes		2,902		—		(1	)		2,901

		323,920		2,057		(3,075	)		322,902

	$	383,191	$	2,156	$	(3,098	)	$	382,249

Proceeds from the sale and maturities of available-for-sale securities were $122,343 and $157,467 for the six months ended July 31, 2012 and 2011, respectively. The Company included in other income, net, realized gains of $85 and $212 for the three and six months ended July 31, 2012, respectively. The Company included in other income, net, realized gains of $23 and $51 for the three and six months ended July 31, 2011, respectively. Amortization of discounts and premiums, net, resulted in charges of $1,243 and $2,478 for the three and six months ended July 31, 2012, respectively. Amortization of discounts and premiums, net, resulted in charges of $2,007 and $4,329 for the three and six months ended July 31, 2011, respectively.

As of July 31, 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 has not been informed by the issuers that accrued interest payments are currently at risk. The Company does not intend 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.