Revenue - Percentages of Sales by Product Line (Details) - Product Line - Sales	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 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	26.00%	34.50%	29.30%	34.70%
Tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	6.60%	9.80%	7.90%	9.90%
Cutting tools
Percentage of Sales by Product Line [Line Items]
Percentage of sales	3.90%	5.80%	4.60%	5.80%
Hydraulics & pneumatics
Percentage of Sales by Product Line [Line Items]
Percentage of sales	5.00%	6.80%	5.80%	6.90%
Material handling
Percentage of Sales by Product Line [Line Items]
Percentage of sales	4.40%	5.90%	5.00%	5.90%
Janitorial supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	10.60%	7.70%	9.50%	7.60%
Electrical supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	4.00%	4.70%	4.30%	4.70%
Welding supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	2.90%	4.20%	3.40%	4.20%
Safety Supplies
Percentage of Sales by Product Line [Line Items]
Percentage of sales	34.00%	17.50%	27.30%	17.40%
Other
Percentage of Sales by Product Line [Line Items]
Percentage of sales	2.60%	3.10%	2.90%	2.90%