Segment Information - Geographic Location (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Consolidated financial information of the Company's operations by geographic location
Net sales	$ 13,835.0	$ 14,805.9	$ 17,025.0
Metals Service Centers
Consolidated financial information of the Company's operations by geographic location
Net sales	13,835.0	14,805.9	17,025.0
Long-lived assets	6,126.3	5,708.5	5,443.3
Metals Service Centers | United States
Consolidated financial information of the Company's operations by geographic location
Net sales	12,933.9	13,786.8	15,978.6
Long-lived assets	5,708.9	5,288.4	5,051.9
Metals Service Centers | Foreign Countries
Consolidated financial information of the Company's operations by geographic location
Net sales	901.1	1,019.1	1,046.4
Long-lived assets	$ 417.4	$ 420.1	$ 391.4