Long-Term Debt - Additional Information (Detail) (USD $) In Millions, unless otherwise specified			9 Months Ended					9 Months Ended												9 Months Ended				9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Ryerson Secured Credit Facility [Member]	Apr. 03, 2013 Ryerson Secured Credit Facility [Member]	Dec. 31, 2012 Ryerson Secured Credit Facility [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] US Subsidiaries [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] Canadian Subsidiaries [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] Minimum [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] Maximum [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] Scenario 2 [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] Scenario 1 [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] Base Rate And Canadian Prime Rate [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] Base Rate And Canadian Prime Rate [Member] Minimum [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] Base Rate And Canadian Prime Rate [Member] Maximum [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] LIBOR and Banker's Acceptance Rate [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] LIBOR and Banker's Acceptance Rate [Member] Minimum [Member]	Sep. 30, 2013 Ryerson Secured Credit Facility [Member] LIBOR and Banker's Acceptance Rate [Member] Maximum [Member]	Sep. 30, 2013 Foreign Debt [Member]	Dec. 31, 2012 Foreign Debt [Member]	Sep. 30, 2013 9% Senior Secured Notes due 2017 [Member]	Oct. 10, 2012 9% Senior Secured Notes due 2017 [Member]	Sep. 30, 2013 11 1/4% Senior Notes due 2018 [Member]	Oct. 10, 2012 11 1/4% Senior Notes due 2018 [Member]	Sep. 30, 2013 2017 and 2018 Notes [Member]	Sep. 30, 2013 2017 and 2018 Notes [Member] Change Of Control Event [Member]	Sep. 30, 2013 Owed To Banks [Member] Foreign Debt [Member] Ryerson China [Member]	Dec. 31, 2012 Owed To Banks [Member] Foreign Debt [Member] Ryerson China [Member]	Sep. 30, 2013 Owed To Banks [Member] Foreign Debt [Member] Acofran [Member]	Dec. 31, 2012 Owed To Banks [Member] Foreign Debt [Member] Acofran [Member]
Debt Instrument [Line Items]
Amended and restated credit facility agreement			$ 1,350	$ 1,350		$ 1,215	$ 135
Credit facility maturity date										Aug. 16, 2017	Apr. 03, 2018
Notes maturity date																				Oct. 15, 2017
Prior to the scheduled maturity date of the 9% Senior Secured Notes			60 days
Debt Instrument Percentage																				9.00%	9.00%		11.25%
Outstanding borrowings			318.5		383.5
Available Credit Facility			291		293													28	21
Letters of credit			24		24													9	8
Weighted average interest rate			1.90%		2.60%																					4.20%	4.80%		11.20%
Line of credit facility, description of collateral			Total credit availability is limited by the amount of eligible accounts receivable and inventory pledged as collateral under the agreement insofar as Ryerson is subject to a borrowing base comprised of the aggregate of these two amounts, less applicable reserves. Eligible accounts receivable, at any date of determination, are comprised of the aggregate value of all accounts directly created by a borrower in the ordinary course of business arising out of the sale of goods or the rendition of services, each of which has been invoiced, with such receivables adjusted to exclude various ineligible accounts, including, among other things, those to which a borrower does not have sole and absolute title and accounts arising out of a sale to an employee, officer, director, or affiliate of a borrower. Eligible inventory, at any date of determination, is comprised of the aggregate value of all inventory owned by a borrower, with such inventory adjusted to exclude various ineligible inventory, including, among other things, any inventory that is classified as “supplies” or is unsaleable in the ordinary course of business and 50% of the value of any inventory that (i) has not been sold or processed within a 180 day period and (ii) which is calculated to have more than 365 days of supply based upon the immediately preceding 6 months consumption.
Percentage of spread over amount available to be borrowed												0.75%	0.50%	1.00%	1.75%	1.50%	2.00%
Commitment fess on amounts not borrowed								0.25%	0.375%
Default bear interest rate			2.00%
Aggregate amount of senior notes issued																					600		300
Maximum percentage of dividend of future net income																								50.00%
Notes redemption date																				Apr. 15, 2015		Oct. 15, 2015
Redemption price as a percentage of principal amount																								100.00%	101.00%
Foreign debt	$ 21.6	$ 21.9																								$ 21.6	$ 21.4	$ 0	$ 0.5