Table:
|  | Fiscal Year |  | Variance in |  |
| --- | --- | --- | --- | --- |
| (In millions, except for percentages) | 2018 | 2017 | Dollars | Percent |
| Net revenues | $2,554 | $2,355 | $199 | 8% |
| Percentage of total net revenues | 53% | 59% |  |  |
| Operating income | $473 | $187 | $286 | 153% |
| Operating margin | 19% | 8% |  |  |
Paragraphs:
Segment operating results
Enterprise Security segment
Revenue increased $199 million primarily due to increases of $331 million in revenue from sales of our network and web security solutions and $36 million from sales of endpoint and information protection solutions, partially offset by a $184 million decrease in revenue as a result of the divestiture of our WSS and PKI solutions. Revenue during fiscal 2018 was also unfavorably affected by a shift in the mix of sales towards subscription and cloud-delivered solutions subject to ratable revenue recognition, which resulted in less in-period recognized revenue and more revenue deferred to the balance sheet as compared to fiscal 2017. Operating income increased $286 million primarily due to higher revenue discussed above, a $51 million decrease in sales and marketing expenses and a $38 million decrease in cost of revenues.
Question:
What is the average Operating income for fiscal 2018 and 2017?