Revenue Recognition - Percentage of Sales by Major Product Lines (Detail)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Product Line
Percentage of sales by major product lines	100.00%	100.00%
Carbon Steel Flat [Member]
Product Line
Percentage of sales by major product lines	25.00%	25.00%
Carbon Steel Plate [Member]
Product Line
Percentage of sales by major product lines	10.00%	12.00%
Carbon Steel Long [Member]
Product Line
Percentage of sales by major product lines	16.00%	16.00%
Stainless Steel Flat [Member]
Product Line
Percentage of sales by major product lines	16.00%	15.00%
Stainless Steel Plate [Member]
Product Line
Percentage of sales by major product lines	5.00%	4.00%
Stainless Steel Long [Member]
Product Line
Percentage of sales by major product lines	5.00%	4.00%
Aluminum Flat [Member]
Product Line
Percentage of sales by major product lines	14.00%	15.00%
Aluminum Plate [Member]
Product Line
Percentage of sales by major product lines	3.00%	2.00%
Aluminum Long [Member]
Product Line
Percentage of sales by major product lines	5.00%	5.00%
Other [Member]
Product Line
Percentage of sales by major product lines	1.00%	2.00%