Income Taxes - Reconciliation of Income Taxes with Amounts Computed by Applying Federal Tax Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Income Tax Expense (Benefit), Effective Income Tax Rate Reconciliation, Amount [Abstract]
Federal income tax expense (benefit) computed at U.S. statutory tax rate, Amount	$ (14.9)	$ (1.6)	$ 40.7
Non-deductible expenses and non-taxable income
Non-deductible expenses and non-taxable income, Amount		2.1	3.0
Equity compensation - (windfall)/shortfall, Amount	0.8
Non-deductible equity compensation, Amount	0.8
Other, Amount	0.7
Cross border tax laws, Amount	(0.1)
U.S. federal tax credits, Amount	(0.3)	(0.4)	(1.7)
Other reconciling items, Amount	0.3	0.4	(1.7)
Domestic state and local income taxes, net of federal effect, Amount	(5.5)	(0.9)	4.7
Foreign tax effects, Amount		0.6	1.2
Worldwide changes in unrecognized tax benefits, Amount	(0.2)	(0.3)	1.1
Total income tax provision (benefit)	$ (16.1)	$ (0.1)	$ 47.3
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Federal income tax expense (benefit) computed at U.S. statutory tax rate, Percentage	21.00%
Non-deductible expenses and non-taxable income
Equity compensation - (windfall)/shortfall, Percentage	(1.10%)
Non-deductible equity compensation, Percentage	(1.10%)
Other, Percentage	(1.00%)
Cross border tax laws, Percentage	0.10%
U.S. federal tax credits, Percentage	0.40%
Other reconciling items, Percentage	(0.40%)
Domestic state and local income taxes, net of federal effect, Percentage	7.70%
Worldwide changes in unrecognized tax benefits, Percentage	0.30%
Total income tax provision (benefit), Percentage	22.60%
Canada [Member]
Non-deductible expenses and non-taxable income
Foreign tax effects, Amount	$ 1.6
Non-deductible expenses and non-taxable income
Foreign tax effects, Percentage	(2.20%)
Other Foreign Jurisdictions [Member]
Non-deductible expenses and non-taxable income
Foreign tax effects, Amount	$ 0.7
Non-deductible expenses and non-taxable income
Foreign tax effects, Percentage	1.00%

Ryerson Holding Corp 10-K