Investments (Tables)

6 Months Ended

Sep. 30, 2012

Summary of available-for-sale securities

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

Summary of amortized cost and estimated fair value of available-for-sale securities, by maturity

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

- Definition

Tabular disclosure of available-for-sale securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 3: http://www.xbrl.org/2003/role/presentationRef

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+ Details