Investments

The Company's investments are intended to establish a high-quality portfolio that preserves principal, meets liquidity needs, avoids inappropriate concentrations, and delivers an appropriate yield in relationship to the Company's investment guidelines and market conditions. The following is a summary of available-for-sale and marketable equity securities at December 31, 2012 (amounts in thousands):



	Available-for-sale Securities
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Government agency bonds	$	522,195	$	458	$	(119	)	$	522,534
Municipal bonds	25,049		205		(28		)	25,226
Auction rate securities	33,509		301		—			33,810
Corporate bonds and debt	715,472		5,311		(34		)	720,749
Marketable equity securities	5,270		—		(917		)	4,353
	$	1,301,495	$	6,275	$	(1,098	)	$	1,306,672

The following is a summary of available-for-sale and marketable equity securities at March 31, 2012 (amounts in thousands):



	Available-for-sale Securities
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Government agency bonds	$	342,025	$	476	$	(397	)	$	342,104
Municipal bonds	19,888		234		—			20,122
Auction rate securities	10,246		—		—			10,246
Corporate bonds and debt	770,891		4,150		(937		)	774,104
Marketable equity securities	5,864		188		(788		)	5,264
	$	1,148,914	$	5,048	$	(2,122	)	$	1,151,840

At December 31, 2012, the Company's available-for-sale debt securities, and marketable equity securities are presented on the condensed consolidated balance sheets as short-term investments of $1,157.0 million and long-term investments of $149.7 million. At March 31, 2012, the Company’s available-for-sale debt securities and marketable equity securities are presented on the condensed consolidated balance sheets as short-term investments of $823.3 million and long-term investments of $328.6 million.

At December 31, 2012, the Company evaluated its investment portfolio and noted unrealized losses of $0.2 million on its debt securities, and $0.9 million on its marketable equity securities, respectively, which were due to fluctuations in interest rates, credit market conditions, and/or market prices. Management does not believe any of the unrealized losses represent an other-than-temporary impairment based on its evaluation of available evidence as of December 31, 2012 and the Company's intent is to hold these investments until these assets are no longer impaired, except for the ARS described above and certain equity investments that are actively being sold. For those debt securities not scheduled to mature until after December 31, 2013, such recovery is not anticipated to occur in the next year and these investments have been classified as long-term investments.

The amortized cost and estimated fair value of the available-for-sale securities at December 31, 2012, by maturity, excluding marketable equity securities of $4.4 million and corporate debt of $5.7 million, which have no contractual maturity, are shown below (amounts in thousands). Expected maturities can differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties, and the Company views its available-for-sale securities as available for current operations.



	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale
Due in one year or less	$	359,924	$	1,594	$	(1	)	$	361,517
Due after one year and through five years	857,067		4,371		(125		)	861,313
Due after five years and through ten years	45,175		98		(55		)	45,218
Due after ten years	28,377		212		—			28,589
	$	1,290,543	$	6,275	$	(181	)	$	1,296,637

The Company had no material realized gains or losses from the sale of available-for-sale marketable equity securities or debt securities during either of the three or nine-month periods ended December 31, 2012 or December 31, 2011.

Marketable Equity Investments

The Company had marketable equity investments with a fair value of $4.4 million as of December 31, 2012. Cash dividends and other distributions of earnings from the investees, if any, are included in other income at the date of record. The Company has classified the shares owned in these companies as marketable securities. At December 31, 2012 the Company had an unrealized loss in other comprehensive income of $0.9 million on these marketable securities. The Company did not recognize an impairment charge on these investments in the three and nine months ended December 31, 2012 compared to impairment charges of $0.2 million and $2.4 million, respectively, in the three and nine months ended December 31, 2011 due to the current market price and active selling of certain shares.

Non-marketable Equity Investments

The Company has certain investments in privately held companies with a carrying value of $7.3 million at December 31, 2012. The investments in privately held companies are accounted for using the cost or the equity method of accounting, as appropriate. Each period the Company evaluates whether an event or change in circumstances has occurred that may indicate an investment has been impaired. If upon further investigation of such events the Company determines the investment has suffered a decline in value that is other than temporary, the Company writes down the investment to its estimated fair value. The Company recognized impairment charges of $0.5 million during the three and nine months ended December 31, 2012. There were no impairment charges recognized on these investments in the three and nine months ended December 31, 2011. These investments are included in other assets on the condensed consolidated balance sheet.