v2.4.0.8

Summary of Significant Accounting Policies , Accounts Receivable (Details) (USD $) In Millions, unless otherwise specified | Dec. 31, 2013 | Dec. 31, 2012
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Accounting Policies [Abstract] |  |
Reserve for sales returns | $ 4.6 | $ 2.3

X
- Definition Reserve for Sales Returns + References No definition available. + Details
Name: | ftnt_ReserveforSalesReturns
Namespace Prefix: | ftnt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Details
Name: | us-gaap_AccountingPoliciesAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration