Investments (Tables)

6 Months Ended

Sep. 30, 2013

Summary of available-for-sale securities

The following is a summary of available-for-sale securities at September 30, 2013 (amounts in thousands):



	Available-for-sale Securities
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Government agency bonds	$	781,230	$	269	$	(5,467	)	$	776,032
Municipal bonds	54,286		60		(575		)	53,771
Auction rate securities	9,829		—		—			9,829
Corporate bonds and debt	796,035		2,902		(1,204		)	797,733
	$	1,641,380	$	3,231	$	(7,246	)	$	1,637,365

The following is a summary of available-for-sale and marketable equity securities at March 31, 2013 (amounts in thousands):



	Available-for-sale Securities
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Government agency bonds	$	558,116	$	335	$	(298	)	$	558,153
Municipal bonds	25,000		146		(8		)	25,138
Auction rate securities	33,459		332		—			33,791
Corporate bonds and debt	680,144		5,137		(159		)	685,122
Marketable equity securities	5,270		239		—			5,509
	$	1,301,989	$	6,189	$	(465	)	$	1,307,713

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, 2013, by contractual maturity, excluding corporate debt of $6.2 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	$	234,539	$	1,133	$	(7	)	$	235,665
Due after one year and through five years	1,280,074		2,098		(2,973		)	1,279,199
Due after five years and through ten years	110,748		—		(4,266		)	106,482
Due after ten years	9,829		—		—			9,829
	$	1,635,190	$	3,231	$	(7,246	)	$	1,631,175

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References

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

-Publisher FASB

-Name Emerging Issues Task Force (EITF)

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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Reference 9: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 115

-Paragraph 19, 20, 21

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 10: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name FASB Staff Position (FSP)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details