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Revenue - Percentages of Sales by Product Line (Details) - Product Line - Sales	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
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	34.20%	34.90%	35.60%
Tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	9.90%	10.00%	10.10%
Cutting tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	5.70%	5.70%	5.80%
Hydraulics and pneumatics
Percentage of Sales by Product Line [Line Items]
Percentage of sales	6.80%	6.80%	6.80%
Material handling
Percentage of Sales by Product Line [Line Items]
Percentage of sales	5.90%	5.80%	5.90%
Janitorial supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	7.80%	7.60%	7.30%
Electrical supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	4.70%	4.70%	4.90%
Welding supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	4.20%	4.10%	4.20%
Safety supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	17.90%	17.20%	16.30%
Other
Percentage of Sales by Product Line [Line Items]
Percentage of sales	2.90%	3.20%	3.10%

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