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Geographic Information - Additional Information (Details) | 12 Months Ended
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Dec. 31, 2015 customer
Segments, Geographical Areas [Abstract] |
Number of customers that represent 5% or more of the consolidated net sales | 0

X
- Definition The number of customers that represent 10% or more of the consolidated net sales. + References No definition available. + Details
Name: | fast_NumberOfCustomers
Namespace Prefix: | fast_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_SegmentsGeographicalAreasAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration