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Sales by Product Line (Percentages Of Sales By Product Line) (Details) | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Revenue from External Customer [Line Items] |  |  |
Total, percentage of sales | 100.00% | 100.00% | 100.00%
Fasteners [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 1967 |  |
Total, percentage of sales | 35.60% | 36.60% | 38.30%
Tools [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 1993 |  |
Total, percentage of sales | 10.10% | 9.90% | 9.50%
Cutting tools [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 1996 |  |
Total, percentage of sales | 5.80% | 5.70% | 5.60%
Hydraulics & pneumatics [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 1996 |  |
Total, percentage of sales | 6.80% | 6.90% | 7.20%
Material handling [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 1996 |  |
Total, percentage of sales | 6.30% | 6.40% | 6.50%
Janitorial supplies [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 1996 |  |
Total, percentage of sales | 7.60% | 7.60% | 7.50%
Electrical supplies [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 1997 |  |
Total, percentage of sales | 4.90% | 4.80% | 4.70%
Welding supplies [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 1997 |  |
Total, percentage of sales | 4.60% | 4.60% | 4.70%
Safety supplies [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 1999 |  |
Total, percentage of sales | 15.20% | 14.90% | 13.90%
Metals [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 2001 |  |
Total, percentage of sales | 0.50% | 0.50% | 0.50%
Direct ship [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 2004 |  |
Total, percentage of sales | 0.50% | 0.50% | 0.40%
Office supplies [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Introduced | 2010 |  |
Total, percentage of sales | 0.10% | 0.10% | 0.10%
Other product line [Member] |  |  |
Revenue from External Customer [Line Items] |  |  |
Total, percentage of sales | 2.00% | 1.50% | 1.10%

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