v3.8.0.1

Balance Sheet Account Details - Narrative - Investment in Consolidated Variable Interest Entities (Details) - USD ($) shares in Millions, $ in Millions |  | 1 Months Ended | 12 Months Ended |  |  |
--- | --- | --- | --- | --- | --- | ---
Feb. 28, 2017 | Jul. 03, 2016 | Jan. 31, 2016 | Dec. 31, 2017 | Jan. 01, 2017 | Jan. 03, 2016 | Feb. 27, 2017 | Jul. 31, 2015 | Dec. 28, 2014
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |
Cash and cash equivalents attributable to variable interest entities |  |  |  | $ 1,225 | $ 735 | $ 769 |  |  | $ 636
Contributions from noncontrolling interest owners |  |  |  | 79 | $ 89 | $ 32 |  |  |
GRAIL, Inc. [Member] |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |
Deemed dividend |  | $ 10 |  |  |  |  |  |  |
Deemed dividend, tax effect |  | $ 10 |  |  |  |  |  |  |
Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |
Cash and cash equivalents attributable to variable interest entities |  |  |  | $ 18 |  |  |  |  |
Variable Interest Entity, Primary Beneficiary [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |
Equity ownership interest percentage |  |  |  |  |  |  | 52.00% |  |
Series A financing |  |  | $ 120 |  |  |  |  |  |
Amount contributed |  |  | 40 |  |  |  |  |  |
Contributions from noncontrolling interest owners |  |  | $ 80 |  |  |  |  |  |
Variable Interest Entity, Primary Beneficiary [Member] | Helix Holdings I, LLC [Member] |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |
Equity ownership interest percentage |  |  |  | 50.00% |  |  |  | 50.00% |
GRAIL Class B [Member] | Variable Interest Entity, Primary Beneficiary [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |
Series A financing | $ 900 |  |  |  |  |  |  |  |
Stock exchanged (in shares) |  |  | 113 |  |  |  |  |  |
GRAIL Class A-1 Convertible [Member] | Variable Interest Entity, Primary Beneficiary [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |
Shares authorized by GRAIL issued to Illumina |  | 98 |  |  |  |  |  |  |
Illumina Class B [Member] | Variable Interest Entity, Primary Beneficiary [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |
Shares authorized by Illumina issued to GRAIL |  | 98 |  |  |  |  |  |  |
Helix Holdings I, LLC [Member] | Variable Interest Entity, Primary Beneficiary [Member] |  |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |  |
Noncontrolling shareholders interest percentage |  |  |  | 50.00% |  |  |  |  |

X
- Definition Deemed Dividend recorded as a result of exchange of a convertible preferred stock financing transaction. + References No definition available. + Details
Name: | ilmn_DeemedDividend
Namespace Prefix: | ilmn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Deemed Dividend, Tax Effect + References No definition available. + Details
Name: | ilmn_DeemedDividendTaxEffect
Namespace Prefix: | ilmn_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Shares Issued By Parent To Less Than Wholly Owned Subsidiary + References No definition available. + Details
Name: | ilmn_SharesIssuedByParentToLessThanWhollyOwnedSubsidiary
Namespace Prefix: | ilmn_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Shares Issued To Parent From Less Than Wholly Owned Subsidiary + References No definition available. + Details
Name: | ilmn_SharesIssuedToParentFromLessThanWhollyOwnedSubsidiary
Namespace Prefix: | ilmn_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section 45 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=82887183&loc=d3e6676-107765 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3044-108585 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.1) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_CashAndCashEquivalentsAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity. + References No definition available. + Details
Name: | us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The parent entity's interest in net assets of the subsidiary, expressed as a percentage. + References No definition available. + Details
Name: | us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix: | us-gaap_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition The cash outflow associated with the acquisition of or advances to an entity that is related to it but not strictly controlled (for example, an unconsolidated subsidiary, affiliate, and joint venture or equity method investment) or the acquisition of an additional interest in a subsidiary (controlled entity). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 13 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3213-108585 + Details
Name: | us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Amount of cash inflow from a noncontrolling interest. Includes, but is not limited to, purchase of additional shares or other increase in noncontrolling interest ownership. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585 + Details
Name: | us-gaap_ProceedsFromMinorityShareholders
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of new stock issued during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 + Details
Name: | us-gaap_StockIssuedDuringPeriodSharesNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:sharesItemType
Balance Type: | na
Period Type: | duration

X
- Definition Equity impact of the value of new stock issued during the period. Includes shares issued in an initial public offering or a secondary public offering. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(28)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.3-04) -URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(29)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_StockIssuedDuringPeriodValueNewIssues
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_VariableInterestEntityLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | dei_LegalEntityAxis=ilmn_GRAILInc.Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_VariableInterestEntitiesByClassificationOfEntityAxis=us-gaap_VariableInterestEntityPrimaryBeneficiaryMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | dei_LegalEntityAxis=ilmn_HelixHoldingsILLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=ilmn_GRAILClassBMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=ilmn_GRAILClassA1ConvertibleMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_StatementClassOfStockAxis=ilmn_IlluminaClassBMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=ilmn_HelixHoldingsILLCMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |