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 September 30, 2012 (amounts in thousands):



	Available-for-sale Securities
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Government agency bonds	$	480,028	$	500	$	(23	)	$	480,505
Municipal bonds	19,825		243		—			20,068
Auction rate securities	34,188		114		—			34,302
Corporate bonds and debt	726,058		5,446		(137		)	731,367
Marketable equity securities	5,270		—		(835		)	4,435
	$	1,265,369	$	6,303	$	(995	)	$	1,270,677

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 September 30, 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 $1,116.7 million and long-term investments of $154.0 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.

The Company believes that, based on its current unrestricted cash, cash equivalents and short-term investment balances, the current lack of liquidity in the credit and capital markets for auction rate securities (ARS) will not have a material impact on its liquidity, cash flow or ability to fund its operations.

At September 30, 2012, the Company evaluated its investment portfolio and noted unrealized losses of $0.2 million on its debt securities, and $0.8 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 September 30, 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 September 30, 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 September 30, 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	$	339,887	$	1,667	$	(9	)	$	341,545
Due after one year and through five years	850,343		4,519		(146		)	854,717
Due after five years and through ten years	35,132		51		(14		)	35,168
Due after ten years	29,055		76		—			29,131
	$	1,254,417	$	6,313	$	(169	)	$	1,260,561

The Company had no realized gains or losses from the sale of available-for-sale marketable equity securities during the three months ended September 30, 2012, compared to a net realized loss of $1.0 million during the three months ended September 30, 2011. The Company had no material gains or losses from sales of available-for-sale debt securities during either the six months ended September 30, 2012 or September 30, 2011.

Marketable Equity Investments

The Company had marketable equity investments in several companies with a fair value of $4.4 million as of September 30, 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. As of September 30, 2012 and March 31, 2012, the Company had an unrealized loss in other comprehensive income of $0.8 million on these marketable securities. The Company did not recognize an impairment charge on these investments in the three and six months ended September 30, 2012 compared to impairment charges of $1.7 million and $2.2 million, respectively, in the three and six months ended September 30, 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 $8.0 million at September 30, 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. At September 30, 2012, the Company determined there were no such impairments. These investments are included in other assets on the condensed consolidated balance sheet.