Marketable Securities (Tables)

12 Months Ended

Jan. 31, 2016

Notes to financial statements [Abstract]

Cash Equivalents and Marketable Securities

	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 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

	January 25, 2015
	Amortized Cost		Unrealized Gain		Unrealized Loss			Estimated Fair Value
	(In millions)
Corporate debt securities	$	2,185	$	3	$	(2	)	$	2,186
Debt securities of United States government agencies	750		—		—			750
Debt securities issued by United States Treasury	534		3		—			537
Asset-backed securities	453		—		—			453
Mortgage backed securities issued by United States government-sponsored enterprises	274		5		(1		)	278
Money market funds	132		—		—			132
Foreign government bonds	85		—		—			85
Total	$	4,413	$	11	$	(3	)	$	4,421
Classified as:
Cash equivalents								$	295
Marketable securities								4,126
Total								$	4,421

The following table provides the breakdown of the investments with unrealized losses as of January 31, 2016:

	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	$	950	$	(3	)	$	80	$	—	$	1,030	$	(3	)
Debt securities issued by United States government agencies	692		(1		)	—		—		692		(1		)
Mortgage backed securities issued by United States government-sponsored enterprises	97		(1		)	31		—		128		(1		)
Total	$	1,739	$	(5	)	$	111	$	—	$	1,850	$	(5	)

Schedule of Cash Equivalents and Marketable Securities Available for Sale

	January 31, 2016				January 25, 2015
	Amortized Cost		Estimated Fair Value		Amortized Cost		Estimated Fair Value
	(In millions)
Less than one year	$	1,619	$	1,619	$	1,570	$	1,570
Due in 1 - 5 years	3,019		3,020		2,720		2,726
Mortgage-backed securities issued by government-sponsored enterprises not due at a single maturity date	34		34		123		125
Total	$	4,672	$	4,673	$	4,413	$	4,421