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 securities at March 31, 2014 (amounts in thousands):



	Available-for-sale Securities
	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Government agency bonds	$	684,451	$	114	$	(3,171	)	$	681,394
Municipal bonds	41,622		101		(14		)	41,709
Auction rate securities	9,825		—		—			9,825
Corporate bonds and debt	941,524		3,247		(805		)	943,966
	$	1,677,422	$	3,462	$	(3,990	)	$	1,676,894

The following is a summary of available-for-sale 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

At March 31, 2014, the Company's available-for-sale debt securities are presented on the consolidated balance sheets as short-term investments of $878.2 million and long-term investments of $798.7 million. At March 31, 2013, the Company’s available-for-sale debt securities and marketable equity securities are presented on the consolidated balance sheets as short-term investments of $1,050.3 million and long-term investments of $257.5 million.

At March 31, 2014, the Company evaluated its investment portfolio and noted unrealized losses of $4.0 million on its debt securities with an aggregated fair value of $782.7 million, which were due primarily to higher interest rates and resulting declines in 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 March 31, 2014 and the Company's intent is to hold these investments until these assets are no longer impaired, except for certain auction rate securities (ARS). For those debt securities not scheduled to mature until after March 31, 2015, 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 March 31, 2014, by contractual maturity, excluding corporate debt of $6.2 million, which has 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	$	210,129	$	1,234	$	—		$	211,363
Due after one year and through five years	1,308,844		2,228		(1,958		)	1,309,114
Due after five years and through ten years	142,434		—		(2,032		)	140,402
Due after ten years	9,825		—		—			9,825
	$	1,671,232	$	3,462	$	(3,990	)	$	1,670,704

The amortized cost and estimated fair value of the available-for-sale securities at March 31, 2013, by maturity, excluding marketable equity securities of $5.5 million and corporate debt of $6.2 million, which have no contractual maturity, are shown below (amounts in thousands).



	Adjusted Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Available-for-sale
Due in one year or less	$	350,349	$	1,933	$	(3	)	$	352,279
Due after one year and through five years	795,952		3,666		(212		)	799,406
Due after five years and through ten years	115,901		116		(250		)	115,767
Due after ten years	28,327		235		—			28,562
	$	1,290,529	$	5,950	$	(465	)	$	1,296,014

The Company had no material realized gains or losses from the sale of available-for-sale marketable equity securities or debt securities during the years ended March 31, 2014, 2013 or 2012.