Supplemental Financial Statement Data Supplemental FS Data - Investments (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Jan. 02, 2015	Jun. 27, 2014
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Current	$ 241	$ 284
Available-for-sale Securities, Noncurrent	224	215
Available-for-sale Securities, Amortized Cost Basis	465	499
Available-for-sale Securities, Gross Unrealized Gain (Loss)	0	0
Available-for-sale Securities, Fair Value	465wdc_AvailableforsaleSecuritiesFairValue	499wdc_AvailableforsaleSecuritiesFairValue
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	159	180
Available-for-sale Securities, Gross Unrealized Gain (Loss)	0	0
Available-for-sale Securities, Fair Value Disclosure	159	180
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	126	88
Available-for-sale Securities, Gross Unrealized Gain (Loss)	0	0
Available-for-sale Securities, Fair Value Disclosure	126	88
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	154	165
Available-for-sale Securities, Gross Unrealized Gain (Loss)	0	0
Available-for-sale Securities, Fair Value Disclosure	154	165
Certificates of Deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	26	66
Available-for-sale Securities, Gross Unrealized Gain (Loss)	0	0
Available-for-sale Securities, Fair Value Disclosure	$ 26	$ 66

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

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Amount of investment in debt and equity securities categorized neither as trading securities nor held-to-maturity securities and intended be sold or mature one year or operating cycle, if longer.

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Investments in debt and equity securities which are categorized neither as held-to-maturity nor trading and which are intended to be sold or mature more than one year from the balance sheet date or operating cycle, if longer. Such securities are reported at fair value; unrealized gains (losses) related to Available-for-sale Securities are excluded from earnings and reported in a separate component of shareholders' equity (other comprehensive income), unless the Available-for-sale security is designated as a hedge or is determined to have had an other than temporary decline in fair value below its amortized cost basis. All or a portion of the unrealized holding gain (loss) of an Available-for-sale security that is designated as being hedged in a fair value hedge is recognized in earnings during the period of the hedge, as are other than temporary declines in fair value below the cost basis for investments in equity securities and debt securities that an entity intends to sell or it is more likely than not that it will be required to sell before the recovery of its amortized cost basis. Other than temporary declines in fair value below the cost basis for debt securities categorized as Available-for-sale that an entity does not intend to sell and for which it is not more likely than not that the entity will be required to sell before the recovery of its amortized cost basis are bifurcated into credit losses and losses related to all other factors. Other than temporary declines in fair value below cost basis related to credit losses are recognized in earnings, and losses related to all other factors are recognized in other comprehensive income.

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Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

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