Marketable Securities

All of our cash equivalents and marketable securities are classified as “available-for-sale” securities. These securities are reported at fair value with the related unrealized gains and losses included in accumulated other comprehensive income (loss), a component of shareholders’ equity, net of tax, and net realized gains and losses recorded in other income (expense), net, on the Consolidated Statements of Income.

We performed an impairment review of our investment portfolio as of January 29, 2017. Factors considered included general market conditions, the duration and extent to which fair value is below cost, and our intent and ability to hold an investment for a sufficient period of time to allow for recovery in value. We also consider specific adverse conditions related to the financial health of and business outlook for an investee, including industry and sector performance, changes in technology, operational and financing cash flow factors, and changes in an investee’s credit rating. Investments that we identify as having an indicator of impairment are subject to further analysis to determine if the investment was other than temporarily impaired. Based on our quarterly impairment review, we concluded that our investments were appropriately valued and that no other-than-temporary impairment charges were necessary on our portfolio of available-for-sale investments as of January 29, 2017.

The following is a summary of cash equivalents and marketable securities as of January 29, 2017 and January 31, 2016:



	January 29, 2017
	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
	(In millions)
Corporate debt securities	$	2,397	$	1	$	(10	)	$	2,388
Debt securities of United States government agencies	1,193		—		(5		)	1,188
Debt securities issued by the United States Treasury	852		—		(2		)	850
Asset-backed securities	490		—		(1		)	489
Money market funds	321		—		—			321
Mortgage backed securities issued by United States government-sponsored enterprises	161		2		(1		)	162
Foreign government bonds	70		—		—			70
Total	$	5,484	$	3	$	(19	)	$	5,468
Classified as:
Cash equivalents								$	436
Marketable securities								5,032
Total								$	5,468



	January 31, 2016
	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
	(In millions)
Corporate debt securities	$	1,903	$	1	$	(3	)	$	1,901
Debt securities of United States government agencies	1,170		1		(1		)	1,170
Debt securities issued by the United States Treasury	800		1		—			801
Asset-backed securities	435		—		—			435
Mortgage backed securities issued by United States government-sponsored enterprises	229		3		(1		)	231
Foreign government bonds	92		—		—			92
Money market funds	43		—		—			43
Total	$	4,672	$	6	$	(5	)	$	4,673
Classified as:
Cash equivalents								$	232
Marketable securities								4,441
Total								$	4,673

The following table provides the breakdown of the investments with unrealized losses as of January 29, 2017:



	Less than 12 Months					12 Months or Greater					Total
	Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses			Fair Value		Gross Unrealized Losses
	(In millions)
Corporate debt securities	$	1,721	$	(10	)	$	55	$	—		$	1,776	$	(10	)
Debt securities issued by United States government agencies	906		(5		)	28		—			934		(5		)
Debt securities issued by the US Treasury	629		(2		)	—		—			629		(2		)
Mortgage backed securities issued by United States government-sponsored enterprises	43		—			35		(1		)	78		(1		)
Asset-backed securities	383		(1		)	3		—			386		(1		)
Total	$	3,682	$	(18	)	$	121	$	(1	)	$	3,803	$	(19	)

The gross unrealized losses related to fixed income securities and were due to changes in interest rates. We have determined that the gross unrealized losses on investment securities as of January 29, 2017 are temporary in nature. Currently, we have the intent and ability to hold our investments with impairment indicators until maturity. Net realized gains were not significant for fiscal years 2017, 2016, and 2015.

The amortized cost and estimated fair value of cash equivalents and marketable securities, which are primarily debt instruments, are classified as available-for-sale as of January 29, 2017 and January 31, 2016 and are shown below by contractual maturity.



	January 29, 2017				January 31, 2016
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
	(In millions)
Less than one year	$	2,209	$	2,209	$	1,619	$	1,619
Due in 1 - 5 years	3,210		3,194		3,019		3,020
Mortgage-backed securities issued by government-sponsored enterprises not due at a single maturity date	65		65		34		34
Total	$	5,484	$	5,468	$	4,672	$	4,673