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Revenue - Percentages of Sales by Product Line (Details) - Product Line - Sales	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Percentage of Sales by Product Line [Line Items]
Percentage of sales	100.00%	100.00%	100.00%
Fasteners
Percentage of Sales by Product Line [Line Items]
Percentage of sales	29.90%	34.20%	34.90%
Tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	8.20%	9.90%	10.00%
Cutting tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	4.70%	5.70%	5.70%
Hydraulics and pneumatics
Percentage of Sales by Product Line [Line Items]
Percentage of sales	5.90%	6.80%	6.80%
Material handling
Percentage of Sales by Product Line [Line Items]
Percentage of sales	5.10%	5.90%	5.80%
Janitorial supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	9.80%	7.80%	7.60%
Electrical supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	4.10%	4.70%	4.70%
Welding supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	3.50%	4.20%	4.10%
Safety supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	25.50%	17.90%	17.20%
Other
Percentage of Sales by Product Line [Line Items]
Percentage of sales	3.30%	2.90%	3.20%

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