Debt - Foreign Debt and Ryerson Holding Notes - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended		12 Months Ended
	Oct. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Foreign debt		$ 25.7	$ 21.9	$ 25.7	$ 21.9
Distribution to repay Ryerson Holding Notes, plus accrued and unpaid interest	344.9	6.6	35.0	6.6	379.9
Foreign Debt [Member]
Debt Instrument [Line Items]
Available credit facility		22	21	22	21
Letters of credit issued by our foreign subsidiaries		4	8	4	8
Owed To Banks [Member] | Ryerson China [Member] | Foreign Debt [Member]
Debt Instrument [Line Items]
Foreign debt		25.7	21.4	25.7	21.4
Weighted average interest rate		4.30%	4.80%	4.30%	4.80%
Owed To Banks [Member] | Acofran [Member] | Foreign Debt [Member]
Debt Instrument [Line Items]
Foreign debt		$ 0	$ 0.5	$ 0	$ 0.5
Weighted average interest rate			11.20%		11.20%