v2.4.1.9

Defined Contribution Plans (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Matching contribution on employee contributions, Percent	50.00%us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Maximum contribtuion percentage of each employee's eligible earnings, Percent	4.00%us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Matching contributions to the RRSP and 401(k) Plans	$ 0.8ftnt_DefinedContributionPlanEmployerMatchingContributionAmount	$ 0.6ftnt_DefinedContributionPlanEmployerMatchingContributionAmount

X

- Definition

Defined Contribution Plan, Employer Matching Contribution, Amount

+ References

No definition available.

+ Details

Name:	ftnt_DefinedContributionPlanEmployerMatchingContributionAmount
Namespace Prefix:	ftnt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Details

Name:	us-gaap_CompensationAndRetirementDisclosureAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanEmployerMatchingContributionPercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

+ References

No definition available.

+ Details

Name:	us-gaap_DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration