Revenue - Percentages of Sales by Product Line (Details) - Product Line - Sales	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
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	30.50%	33.70%	29.70%	34.30%
Tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	8.50%	10.20%	8.10%	10.00%
Cutting tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	4.70%	5.70%	4.60%	5.80%
Hydraulics & pneumatics
Percentage of Sales by Product Line [Line Items]
Percentage of sales	6.10%	6.80%	5.90%	6.90%
Material handling
Percentage of Sales by Product Line [Line Items]
Percentage of sales	5.10%	5.90%	5.10%	5.90%
Janitorial supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	10.70%	8.00%	9.90%	7.70%
Electrical supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	3.90%	4.60%	4.10%	4.70%
Welding supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	3.50%	4.20%	3.50%	4.20%
Safety Supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	23.80%	18.20%	26.10%	17.60%
Other
Percentage of Sales by Product Line [Line Items]
Percentage of sales	3.20%	2.70%	3.00%	2.90%