Common stock capital shares reserved for future issuance decrease.

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Dividends declared.

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Share based compensation arrangement by share based payment award duration of offering period.

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Share based compensation arrangement by share based payment award duration of purchase period.

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Share based compensation arrangement by share based payment award maximum number value per employee.

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- Definition

Share based compensation arrangement by share based payment award number of purchase periods.

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- Definition

Share based compensation arrangement by share based payment award number of shares authorized per participant.

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Value of accelerated share repurchase agreement forward contract value.

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Final price paid per share for the purchase of the targeted number of shares, determined by an average market price over a fixed period of time.

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Amount of cash receipt from (payment to) bank; or stock received from (issuance to) bank in the settlement of the accelerated share repurchase agreement.

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Aggregate dividends declared during the period for each share of common stock outstanding.

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Date the declared dividend will be paid, in CCYY-MM-DD format.

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Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

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Unrecognized cost of unvested share-based compensation awards.

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Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The cash outflow to reacquire common and preferred stock.

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-Glossary Financing Activities

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Cash outflow in the form of capital distributions and dividends to common shareholders, preferred shareholders and noncontrolling interests.

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- Definition

The maximum number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) permitted to be issued by an entity's charter and bylaws.

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Total number of nonredeemable preferred shares (or preferred stock redeemable solely at the option of the issuer) issued to shareholders (includes related preferred shares that were issued, repurchased, and remain in the treasury). May be all or portion of the number of preferred shares authorized. Excludes preferred shares that are classified as debt.

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Aggregate share number for all nonredeemable preferred stock (or preferred stock redeemable solely at the option of the issuer) held by stockholders. Does not include preferred shares that have been repurchased.

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Percentage of vesting of share-based compensation awards.

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Discount rate from fair value on purchase date that participants pay for shares.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The highest quantity of shares an employee can purchase under the plan per period.

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- Definition

Number of additional shares authorized for issuance under an established share-based compensation plan.

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No definition available.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Purchase price of common stock expressed as a percentage of its fair value.

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Number of shares that have been repurchased and retired during the period.

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Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

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Amount of stock repurchase plan authorized.

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Total cost of shares repurchased divided by the total number of shares repurchased.

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Stockholders' Equity - Additional Information (Detail) (USD $)	12 Months Ended			143 Months Ended	0 Months Ended
	Apr. 24, 2015	Apr. 25, 2014	Apr. 26, 2013	Apr. 24, 2015	May 20, 2015	Sep. 05, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation expense related to equity awards	$ 358,700,000			$ 358,700,000
Unrecognized compensation expense will be amortized on a straight-line basis over a weighted-average remaining period, in years	2 years 2 months 12 days
Stock repurchase program, authorized amount	9,600,000,000			9,600,000,000
Allocation of purchase price of share repurchases	1,165,200,000	1,881,500,000	590,000,000
Repurchase of common stock, shares	29,600,000	47,300,000	18,100,000	214,000,000
Average price of common stock repurchased under repurchase program	$ 39.30	$ 39.78	$ 32.68	$ 33.48
Aggregate purchase price of common stock authorized under repurchase program				7,200,000,000us-gaap_PaymentsForRepurchaseOfEquity
Prepayment to purchase shares of common stock		750,000,000
Accelerated share repurchases, weighted-average price		$ 39.13
Preferred stock, shares authorized	5,000,000us-gaap_PreferredStockSharesAuthorized	5,000,000us-gaap_PreferredStockSharesAuthorized		5,000,000us-gaap_PreferredStockSharesAuthorized
Preferred stock, shares issued	0us-gaap_PreferredStockSharesIssued	0us-gaap_PreferredStockSharesIssued		0us-gaap_PreferredStockSharesIssued
Preferred stock, shares outstanding	0us-gaap_PreferredStockSharesOutstanding	0us-gaap_PreferredStockSharesOutstanding		0us-gaap_PreferredStockSharesOutstanding
Dividends declared			0ntap_DividendsDeclared
Dividends paid	207,400,000us-gaap_PaymentsOfDividends	202,300,000us-gaap_PaymentsOfDividends	0us-gaap_PaymentsOfDividends
Cash dividends declared, per common share	$ 0.66	$ 0.60
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash dividends declared, per common share					$ 0.18
Cash dividend payable date					Jul. 23, 2015
Cash dividend record date					Jul. 10, 2015
Additional Paid-in Capital
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocation of purchase price of share repurchases	812,800,000	813,400,000	176,200,000
Value of forward contract		13,900,000
Dividends paid	52,000,000	50,400,000
Retained Earnings
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocation of purchase price of share repurchases	352,400,000	1,068,000,000	413,800,000
Dividends paid	155,400,000	151,900,000
Accelerated Share Repurchase Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Repurchase of common stock, shares		19,200,000
Share Repurchase Authorization Increase
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock repurchase program, authorized amount	2,500,000,000			2,500,000,000
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Additional shares authorized						5,000,000
Shares available for grant	8,900,000			8,900,000
Share offering period for eligible employees	24 months
Number of consecutive purchase periods	4
Duration of purchase period	6 months
Percentage of discount from quoted market price, employees entitled to buy shares (ESPP)	15.00%
1999 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in number of shares reserved for issuance for every share subject to a full value award	2
Number of shares that may be granted to a participant in any calendar year	1,000,000
Maximum initial value of performance units a participant may receive	$ 5,000,000
Number of performance shares a participant may receive in a calendar year	1,000,000
Additional shares authorized	7,500,000
Shares available for grant	12,700,000			12,700,000
1999 Stock Option Plan \| Stock Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Purchase price of common stock, percentage	100.00%
Award granted, vesting period	4 years
Options granted period term	7 years
1999 Stock Option Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award granted, vesting period	4 years
Vesting rate	25.00%