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Marketable Securities - Additional Information (Detail) (USD $) | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2013 | Sep. 30, 2012 | Sep. 30, 2013 | Sep. 30, 2012
Financial Instruments And Marketable Securities [Abstract] |  |  |  |
Dollar value of transfers between levels | $ 0 | $ 0 | $ 0 | $ 0

X
- Details
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Namespace Prefix: | fast_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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- Definition Marketable Security Level Transfers + References No definition available. + Details
Name: | fast_MarketableSecurityLevelTransfers
Namespace Prefix: | fast_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration