v3.8.0.1

Balance Sheet Account Details - Narrative - Deconsolidation of GRAIL, Inc. (Details) - USD ($) shares in Millions, $ in Millions |  | 1 Months Ended | 2 Months Ended | 3 Months Ended | 12 Months Ended |
--- | --- | --- | --- | --- | --- | ---
Feb. 28, 2017 | Jan. 31, 2016 | Feb. 28, 2017 | Jul. 02, 2017 | Dec. 31, 2017 | Jan. 01, 2017 | Jan. 03, 2016 | Feb. 27, 2017
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Proceeds from sale of GRAIL preferred stock |  |  |  |  | $ 278 |  |  |
Payments for additional GRAIL shares purchased by Illumina |  |  |  |  | 29 | $ 14 | $ 6 |
Gain on deconsolidation of GRAIL | $ 453 |  |  |  | $ 453 |  |  |
Portion of gain on deconsolidation related to remeasurement of Company's retained equity interest | $ 159 |  |  |  |  |  |  |
GRAIL, Inc. [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Cost-method investment ownership percentage | 19.00% |  | 19.00% | 17.00% |  |  |  |
Cost-method investment voting interest percentage | 13.00% |  | 13.00% | 12.00% |  |  |  |
GRAIL Class B [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Strategic Investment Shares Purchased |  |  |  | 3 |  |  |  |
Payments for additional GRAIL shares purchased by Illumina |  |  |  | $ 14 |  |  |  |
Remaining shares of GRAIL owned by Illumina |  |  |  |  | 3 |  |  |
GRAIL Class A Preferred [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Remaining shares of GRAIL owned by Illumina |  |  |  |  | 5 |  |  |
GRAIL Class A Common [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Remaining shares of GRAIL owned by Illumina |  |  |  |  | 78 |  |  |
Variable Interest Entity, Primary Beneficiary [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
GRAIL Series B preferred financing |  | $ 120 |  |  |  |  |  |
Proceeds from sale of GRAIL preferred stock | $ 278 |  |  |  |  |  |  |
Equity ownership interest percentage |  |  |  |  |  |  |  | 52.00%
Percentage of entity's losses absorbed |  |  | 50.00% |  |  |  |  |
Variable Interest Entity, Primary Beneficiary [Member] | GRAIL Class B [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
GRAIL Series B preferred financing | $ 900 |  |  |  |  |  |  |
Variable Interest Entity, Primary Beneficiary [Member] | GRAIL Class A Preferred [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Shares repurchased by GRAIL from Illumina | 35 |  |  |  |  |  |  |
Variable Interest Entity, Primary Beneficiary [Member] | GRAIL Class A-1 Convertible [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Shares repurchased by GRAIL from Illumina | 34 |  |  |  |  |  |  |
Other Assets [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Cost-method investments |  |  |  |  | $ 250 | $ 57 |  |
Other Assets [Member] | GRAIL, Inc. [Member] |  |  |  |  |  |  |  |
Variable Interest Entity [Line Items] |  |  |  |  |  |  |  |
Cost-method investments |  |  |  |  | $ 185 |  |  |

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