Employee Benefit Plans	12 Months Ended
Dec. 31, 2017
Deferred Compensation Arrangements [Abstract]
Employee Benefit Plans	Employee Benefit Plans Retirement Plan We have a 401(k) savings plan covering substantially all of our employees in the United States. Our contributions to the plan are discretionary. During the years ended December 31, 2017, January 1, 2017, and January 3, 2016, we made matching contributions of $17 million, $14 million, and $12 million, respectively. Deferred Compensation Plan The Illumina, Inc. Deferred Compensation Plan (the Plan) allows senior level employees to contribute up to 80% of their base salary and 100% of their variable cash compensation, and members of the board of directors to contribute up to 100% of their director fees and equity awards. Under the Plan, we credit the participants’ contributions with earnings that reflect the performance of certain independent investment funds. On a discretionary basis, we may also make employer contributions to participant accounts in any amount determined by us. The vesting schedules of employer contributions are at the sole discretion of the Compensation Committee. However, all employer contributions shall become 100% vested upon the occurrence of the participant’s disability, death or retirement or a change in control of Illumina. The benefits under this plan are unsecured. Participants are generally eligible to receive payment of their vested benefit at the end of their elected deferral period or after termination of their employment for any reason or at a later date to comply with the restrictions of Section 409A. We also established a rabbi trust for the benefit of the participants under the Plan, and have included the assets of the rabbi trust in the consolidated balance sheets. As of December 31, 2017 and January 1, 2017, the assets of the trust were $35 million and $31 million, respectively, and our liabilities were $33 million and $29 million, respectively. The assets and liabilities are classified as other assets and accrued liabilities, respectively, on the consolidated balance sheets. Changes in the values of the assets held by the rabbi trust are recorded in other income (expense), net in the consolidated statements of income, and changes in the values of the deferred compensation liabilities are recorded in cost of revenue or operating expenses.

Employee Benefit Plans

Retirement Plan

We have a 401(k) savings plan covering substantially all of our employees in the United States. Our contributions to the plan are discretionary. During the years ended December 31, 2017, January 1, 2017, and January 3, 2016, we made matching contributions of $17 million, $14 million, and $12 million, respectively.

Deferred Compensation Plan

The Illumina, Inc. Deferred Compensation Plan (the Plan) allows senior level employees to contribute up to 80% of their base salary and 100% of their variable cash compensation, and members of the board of directors to contribute up to 100% of their director fees and equity awards. Under the Plan, we credit the participants’ contributions with earnings that reflect the performance of certain independent investment funds. On a discretionary basis, we may also make employer contributions to participant accounts in any amount determined by us. The vesting schedules of employer contributions are at the sole discretion of the Compensation Committee. However, all employer contributions shall become 100% vested upon the occurrence of the participant’s disability, death or retirement or a change in control of Illumina. The benefits under this plan are unsecured. Participants are generally eligible to receive payment of their vested benefit at the end of their elected deferral period or after termination of their employment for any reason or at a later date to comply with the restrictions of Section 409A.

We also established a rabbi trust for the benefit of the participants under the Plan, and have included the assets of the rabbi trust in the consolidated balance sheets. As of December 31, 2017 and January 1, 2017, the assets of the trust were $35 million and $31 million, respectively, and our liabilities were $33 million and $29 million, respectively. The assets and liabilities are classified as other assets and accrued liabilities, respectively, on the consolidated balance sheets. Changes in the values of the assets held by the rabbi trust are recorded in other income (expense), net in the consolidated statements of income, and changes in the values of the deferred compensation liabilities are recorded in cost of revenue or operating expenses.