Long-Term Debt - Foreign Debt - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Dec. 31, 2021
Debt Instrument [Line Items]
Foreign debt	$ 22.9	$ 27.0
Foreign Debt [Member]
Debt Instrument [Line Items]
Available credit facility	24.0	20.0
Letters of credit issued by our foreign subsidiaries	5.0	6.0
Foreign Debt [Member] | Owed to Banks [Member] | Ryerson China [Member]
Debt Instrument [Line Items]
Foreign debt	$ 22.9	$ 27.0
Weighted average interest rate	3.40%	3.60%