Revenue - Percentages of Sales by Product Line (Details) - Product Line - Sales	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Percentage of Sales by Product Line [Line Items]
Percentage of sales	100.00%	100.00%	100.00%	100.00%
Fasteners
Percentage of Sales by Product Line [Line Items]
Percentage of sales	33.40%	30.50%	33.20%	29.70%
Tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	8.50%	8.50%	8.60%	8.10%
Cutting tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	5.00%	4.70%	5.00%	4.60%
Hydraulics & pneumatics
Percentage of Sales by Product Line [Line Items]
Percentage of sales	6.50%	6.10%	6.40%	5.90%
Material handling
Percentage of Sales by Product Line [Line Items]
Percentage of sales	5.50%	5.10%	5.50%	5.10%
Janitorial supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	8.30%	10.70%	8.20%	9.90%
Electrical supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	4.30%	3.90%	4.30%	4.10%
Welding supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	3.80%	3.50%	3.80%	3.50%
Safety Supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	21.10%	23.80%	21.20%	26.10%
Other
Percentage of Sales by Product Line [Line Items]
Percentage of sales	3.60%	3.20%	3.80%	3.00%