Financial Instruments

The following is a summary of cash equivalents and available-for-sale securities as of the end of the periods presented:



	September 30, 2017									April 1, 2017
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value		Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
Money market funds	$	323,034	$	—	$	—		$	323,034	$	298,307	$	—	$	—		$	298,307
Financial institution
securities	580,717		—		—			580,717		348,797		—		—			348,797
Non-financial institution
securities	418,879		744		(277		)	419,346		409,109		647		(496		)	409,260
U.S. government and	—
agency securities	95,793		5		(134		)	95,664		130,749		8		(223		)	130,534
Foreign government and
agency securities	264,788		—		—			264,788		322,172		—		(51		)	322,121
Mortgage-backed securities	1,201,005		5,409		(9,763		)	1,196,651		1,186,732		3,527		(14,757		)	1,175,502
Asset-backed securities	219,255		480		(478		)	219,257		220,033		404		(686		)	219,751
Debt mutual funds	101,350		—		(10,860		)	90,490		101,350		—		(12,674		)	88,676
Bank loans	157,510		643		(254		)	157,899		153,281		839		(106		)	154,014
Commercial mortgage-
backed securities	247,390		199		(3,572		)	244,017		221,504		146		(3,679		)	217,971
	$	3,609,721	$	7,480	$	(25,338	)	$	3,591,863	$	3,392,034	$	5,571	$	(32,672	)	$	3,364,933

The following tables show the fair values and gross unrealized losses of the Company’s investments, aggregated by investment category, for individual securities that have been in a continuous unrealized loss position for the length of time specified, as of September 30, 2017 and April 1, 2017:



	September 30, 2017
	Less Than 12 Months					12 Months or Greater					Total
(In thousands)	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Non-financial institution securities	$	62,033	$	(210	)	$	5,606	$	(67	)	$	67,639	$	(277	)
U.S. government and
agency securities	34,015		(125		)	5,130		(9		)	39,145		(134		)
Mortgage-backed securities	730,974		(6,516		)	157,026		(3,247		)	888,000		(9,763		)
Asset-backed securities	135,560		(464		)	4,757		(14		)	140,317		(478		)
Debt mutual funds	—		—			90,490		(10,860		)	90,490		(10,860		)
Bank loans	30,107		(254		)	—		—			30,107		(254		)
Commercial mortgage-
backed securities	119,843		(893		)	60,028		(2,679		)	179,871		(3,572		)
	$	1,112,532	$	(8,462	)	$	323,037	$	(16,876	)	$	1,435,569	$	(25,338	)



	April 1, 2017
	Less Than 12 Months					12 Months or Greater					Total
(In thousands)	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
Non-financial institution securities	$	68,850	$	(492	)	$	1,022	$	(4	)	$	69,872	$	(496	)
U.S. government and
agency securities	64,895		(223		)	—		—			64,895		(223		)
Mortgage-backed securities	811,058		(11,872		)	139,931		(2,885		)	950,989		(14,757		)
Asset-backed securities	119,845		(651		)	4,689		(35		)	124,534		(686		)
Debt mutual funds	—		—			88,676		(12,674		)	88,676		(12,674		)
Bank loans	15,139		(106		)	—		—			15,139		(106		)
Foreign government and
agency securities	64,857		(51		)	—		—			64,857		(51		)
Commercial mortgage-
backed securities	165,393		(1,706		)	24,362		(1,973		)	189,755		(3,679		)
	$	1,310,037	$	(15,101	)	$	258,680	$	(17,571	)	$	1,568,717	$	(32,672	)

As of September 30, 2017, the gross unrealized losses that had been outstanding for less than twelve months were primarily related to mortgage-backed securities due to the general rising of the interest-rate environment, although the percentage of such losses to the total estimated fair value of the mortgage-backed securities was relatively insignificant. The gross unrealized losses that had been outstanding for more than twelve months were primarily related to debt mutual funds, mortgage-backed securities and commercial mortgage-backed securities, which were primarily due to the general rising of the interest-rate environment and foreign currency movement.

The Company reviewed the investment portfolio and determined that the gross unrealized losses on these investments as of September 30, 2017 and April 1, 2017 were temporary in nature as evidenced by the fluctuations in the gross unrealized losses within the investment categories. These investments are highly rated by the credit rating agencies, there have been no defaults on any of these securities and we have received interest payments as they become due. Therefore, the Company believes that it will be able to collect both principal and interest amount due to the Company. Additionally, in the past several years a portion of the Company's investment in the mortgage-backed securities were redeemed or prepaid by the debtors at par. Furthermore, the aggregate of individual unrealized losses that had been outstanding for twelve months or more were not significant as of September 30, 2017 and April 1, 2017, the majority of which were related to debt mutual funds due to foreign currency and interest rate fluctuations. The Company neither intends to sell these investments nor concludes that it is more-likely-than-not that it will have to sell them until recovery of their carrying values.

The amortized cost and estimated fair value of marketable debt securities (financial institution securities, non-financial institution securities, U.S. and foreign government and agency securities, asset-backed securities, bank loans, mortgage-backed securities and commercial mortgage-backed securities), by contractual maturity, are shown in the table below. Actual maturities may differ from contractual maturities because issuers may have the right to call or prepay obligations without call or prepayment penalties.



	September 30, 2017
(In thousands)	Amortized Cost		Estimated Fair Value
Due in one year or less	$	1,200,344	$	1,200,345
Due after one year through five years	469,451		467,424
Due after five years through ten years	312,956		312,503
Due after ten years	1,202,586		1,198,067
	$	3,185,337	$	3,178,339

As of September 30, 2017, $1.93 billion of marketable debt securities with contractual maturities of greater than one year were classified as short-term investments. Additionally, the above table did not include investments in money market and mutual funds because these funds do not have specific contractual maturities.

Certain information related to available-for-sale securities is as follows:



	Three Months Ended						Six Months Ended
(In thousands)	September 30, 2017			October 1, 2016			September 30, 2017			October 1, 2016
Proceeds from sale of available-for-sale securities	$	149,497		$	153,871		$	269,419		$	253,345
Gross realized gains on sale of available-for-sale securities	$	519		$	762		$	1,351		$	1,427
Gross realized losses on sale of available-for-sale securities	(209		)	(92		)	(595		)	(604		)
Net realized gains on sale of available-for-sale securities	$	310		$	670		$	756		$	823
Amortization of premiums on available-for-sale securities	$	4,691		$	7,414		$	10,213		$	14,175

The cost of securities matured or sold is based on the specific identification method.