The Company holds investments in marketable debt securities that are classified and accounted for as available-for-sale and are remeasured on a recurring basis. For information regarding the valuation techniques and inputs used in the fair value measurements, refer to Note 1 to the consolidated financial statements included in the Company's Annual Report on Form 10-K for the fiscal year ended April 26, 2019.

The following tables summarize the Company's investments in available-for-sale debt securities by significant investment category and the related consolidated balance sheet classification at October 25, 2019 and April 26, 2019:


	October 25, 2019
	Valuation												Balance Sheet Classification
(in millions)	Cost		Unrealized Gains		Unrealized Losses		Fair Value		Investments		Other Assets
Level 1:
U.S. government and agency securities	$	565	$	15	$	—	$	580	$	580	$	—
Level 2:
Corporate debt securities	3,814		43		(16)		3,841		3,841		—
U.S. government and agency securities	858		—		(1)		857		857		—
Mortgage-backed securities	634		11		(13)		632		632		—
Non-U.S. government and agency securities	13		—		—		13		13		—
Other asset-backed securities	514		2		(3)		513		513		—
Total Level 2	5,833		56		(33)		5,856		5,856		—
Level 3:

Auction rate securities	47		—		(3)		44		—		44

Total available-for-sale debt securities	$	6,445	$	71	$	(36)	$	6,480	$	6,436	$	44


	April 26, 2019
	Valuation												Balance Sheet Classification
(in millions)	Cost		Unrealized Gains		Unrealized Losses		Fair Value		Investments		Other Assets
Level 1:
U.S. government and agency securities	$	529	$	1	$	(7)	$	523	$	523	$	—
Level 2:
Corporate debt securities	3,500		14		(21)		3,493		3,493		—
U.S. government and agency securities	387		1		(7)		381		381		—
Mortgage-backed securities	537		3		(20)		520		520		—
Non-U.S. government and agency securities	11		—		—		11		11		—
Other asset-backed securities	529		1		(3)		527		527		—
Total Level 2	4,964		19		(51)		4,932		4,932		—
Level 3:
Auction rate securities	47		—		(3)		44		—		44
Total available-for-sale debt securities	$	5,540	$	20	$	(61)	$	5,499	$	5,455	$	44

The following tables present the gross unrealized losses and fair values of the Company’s available-for-sale debt securities that have been in a continuous unrealized loss position deemed to be temporary, aggregated by investment category at October 25, 2019 and April 26, 2019:


	October 25, 2019
	Less than 12 months						More than 12 months
(in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. government and agency securities	$	140	$	—	$	180	$	(1)
Corporate debt securities	484		(9)		129		(7)
Mortgage-backed securities	91		(1)		89		(12)
Non-U.S. government and agency securities	2		—		—		—
Other asset-backed securities	167		(1)		156		(2)
Auction rate securities	—		—		44		(3)
Total	$	884	$	(11)	$	598	$	(25)


	April 26, 2019
	Less than 12 months						More than 12 months
(in millions)	Fair Value		Unrealized Losses		Fair Value		Unrealized Losses
U.S. government and agency securities	$	130	$	(1)	$	649	$	(13)
Corporate debt securities	582		(5)		1,153		(16)
Mortgage-backed securities	73		(1)		250		(19)

Other asset-backed securities	290		(2)		85		(1)
Auction rate securities	—		—		44		(3)
Total	$	1,075	$	(9)	$	2,181	$	(52)

The Company reviews the fair value hierarchy classification on a quarterly basis. Changes in the ability to observe valuation inputs may result in a reclassification of levels for certain securities within the fair value hierarchy. The Company’s policy is to recognize transfers into and out of levels within the fair value hierarchy at the end of the fiscal quarter in which the actual event or change in circumstances that caused the transfer occurs. There were no transfers between Level 1, Level 2, or Level 3 during the three and six months ended October 25, 2019 and October 26, 2018. When a determination is made to classify an asset or

liability within Level 3, the determination is based upon the significance of the unobservable inputs to the overall fair value measurement.

There were no purchases, sales, settlements, or gains or losses recognized in earnings or other comprehensive income for available-for-sale securities classified as Level 3 during the three and six months ended October 25, 2019 and October 26, 2018.


	Three months ended						Six months Ended
(in millions)	October 25, 2019		October 26, 2018		October 25, 2019		October 26, 2018
Proceeds from sales	$	1,691	$	804	$	3,258	$	1,916
Gross realized gains	4		2		8		8
Gross realized losses	(4)		(12)		(12)		(19)

Credit losses represent the difference between the present value of cash flows expected to be collected on certain mortgage-backed securities and auction rate securities and the amortized cost of these securities. Based on the Company’s assessment of the credit quality of the underlying collateral and credit support available to each of the remaining securities in which the Company is invested, the Company believes it has recognized all necessary other-than-temporary impairments, as the Company does not have the intent to sell, nor is it more likely than not that the Company will be required to sell, before recovery of the amortized cost.

At October 25, 2019 and April 26, 2019, the credit loss portion of other-than-temporary impairments on debt securities was not significant. No available-for-sale securities were sold for significantly less than carrying value during the three and six months ended October 25, 2019 and October 26, 2018.

The October 25, 2019 balance of available-for-sale debt securities by contractual maturity is shown in the following table. Within the table, maturities of mortgage-backed securities have been allocated based upon timing of estimated cash flows assuming no change in the current interest rate environment. Actual maturities may differ from contractual maturities because the issuers of the securities may have the right to prepay obligations without prepayment penalties.


(in millions)	October 25, 2019
Due in one year or less	$	1,975
Due after one year through five years	2,578
Due after five years through ten years	1,881
Due after ten years	46
Total	$	6,480

The Company holds investments in equity securities without readily determinable fair values, investments accounted for under the equity method, and other investments. Equity method investments and investments without readily determinable fair values are included within Level 3 of the fair value hierarchy due to the use of significant unobservable inputs to determine fair value. To determine the fair value of these investments, the Company uses all pertinent financial information available related to the investees, including financial statements, market participant valuations from recent and proposed equity offerings, and other third-party data.

The following table summarizes the Company's equity and other investments at October 25, 2019 and April 26, 2019, which are classified as other assets in the consolidated balance sheets:


(in millions)	October 25, 2019		April 26, 2019

Investments without readily determinable fair values	$	366	$	308
Equity method and other investments	66		64
Total equity and other investments	$	432	$	372

The table below includes activity related to the Company’s portfolio of equity and other investments. Gains and losses on equity and other investments are recognized in other non-operating income, net in the consolidated statements of income.


	Three months ended						Six months ended
(in millions)	October 25, 2019		October 26, 2018		October 25, 2019		October 26, 2018
Proceeds from sales	$	—	$	—	$	2	$	908
Gross gains	14		9		14		123
Gross losses	—		(13)		—		(29)
Impairment losses recognized	(2)		(12)		(3)		(12)