Condensed Consolidating Guarantor Financial Statements - Condensed Consolidating Statement of Comprehensive Income (Unaudited) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Schedule of Condensed Consolidating Statement of Comprehensive Income [Line Items]
Net sales	$ 947.9	$ 859.8	$ 2,753.8	$ 2,657.8
Cost of materials sold	798.4	704.7	2,302.2	2,188.4
Gross profit	149.5	155.1	451.6	469.4
Warehousing, delivery, selling, general and administrative	154.2	119.6	392.4	362.7
Restructuring and other charges				2.1
Gain on sale of assets	(1.3)		(1.3)
Impairment charges on fixed assets and goodwill		1.1		8.8
Operating profit (loss)	(3.4)	34.4	60.5	95.8
Other income and (expense), net	(8.5)	(1.1)	(8.2)	2.1
Interest and other expense on debt	(27.9)	(27.1)	(82.8)	(83.3)
Income (loss) before income taxes	(39.8)	6.2	(30.5)	14.6
Provision (benefit) for income taxes	(13.4)	2.9	(7.8)	6.2
Net income (loss)	(26.4)	3.3	(22.7)	8.4
Less: Net loss attributable to noncontrolling interest	(0.8)	(1.0)	(2.6)	(4.9)
Net income (loss) attributable to Ryerson Inc.	(25.6)	4.3	(20.1)	13.3
Comprehensive income (loss)	(33.7)	8.6	(33.7)	6.9
Less: Comprehensive loss attributable to noncontrolling interest	(0.8)	(1.2)	(2.7)	(4.9)
Comprehensive income (loss) attributable to Ryerson Inc.	(32.9)	9.8	(31.0)	11.8
Parent [Member]
Schedule of Condensed Consolidating Statement of Comprehensive Income [Line Items]
Warehousing, delivery, selling, general and administrative	1.0	1.3	3.7	3.8
Operating profit (loss)	(1.0)	(1.3)	(3.7)	(3.8)
Interest and other expense on debt	(3.7)	(3.3)	(11.2)	(11.9)
Interest expense on intercompany loans	(6.9)	(7.4)	(21.9)	(19.4)
Income (loss) before income taxes	(11.6)	(12.0)	(36.8)	(35.1)
Provision (benefit) for income taxes	23.8	(8.6)	8.8	(13.0)
Equity in (earnings) loss of subsidiaries	(9.8)	(7.7)	(25.5)	(35.4)
Net income (loss)	(25.6)	4.3	(20.1)	13.3
Net income (loss) attributable to Ryerson Inc.	(25.6)	4.3	(20.1)	13.3
Comprehensive income (loss)	(32.9)	9.8	(31.0)	11.8
Comprehensive income (loss) attributable to Ryerson Inc.	(32.9)	9.8	(31.0)	11.8
Joseph T. Ryerson [Member]
Schedule of Condensed Consolidating Statement of Comprehensive Income [Line Items]
Net sales	806.3	726.2	2,342.1	2,241.9
Cost of materials sold	689.4	599.2	1,984.5	1,857.4
Gross profit	116.9	127.0	357.6	384.5
Warehousing, delivery, selling, general and administrative	129.7	91.3	318.2	278.9
Impairment charges on fixed assets and goodwill		1.1		2.0
Operating profit (loss)	(12.8)	34.6	39.4	103.6
Other income and (expense), net	(11.1)		(11.0)	0.2
Interest and other expense on debt	(23.5)	(23.1)	(69.5)	(69.2)
Interest income on intercompany loans	5.1	5.5	16.2	13.6
Income (loss) before income taxes	(42.3)	17.0	(24.9)	48.2
Provision (benefit) for income taxes	(23.2)	12.2	(12.9)	18.3
Equity in (earnings) loss of subsidiaries	(13.1)	(4.7)	(31.4)	(14.3)
Net income (loss)	(6.0)	9.5	19.4	44.2
Net income (loss) attributable to Ryerson Inc.	(6.0)	9.5	19.4	44.2
Comprehensive income (loss)	(2.1)	10.3	23.2	46.7
Comprehensive income (loss) attributable to Ryerson Inc.	(2.1)	10.3	23.2	46.7
Guarantor [Member]
Schedule of Condensed Consolidating Statement of Comprehensive Income [Line Items]
Net sales	714.4	596.5	1,952.8	1,800.0
Cost of materials sold	701.0	585.7	1,914.5	1,766.2
Gross profit	13.4	10.8	38.3	33.8
Warehousing, delivery, selling, general and administrative	6.1	6.3	18.2	17.5
Operating profit (loss)	7.3	4.5	20.1	16.3
Interest income on intercompany loans	1.8	1.9	5.7	5.8
Income (loss) before income taxes	9.1	6.4	25.8	22.1
Provision (benefit) for income taxes	(13.7)	5.3	(3.7)	8.3
Equity in (earnings) loss of subsidiaries	(1.9)	(4.1)	(2.0)	(0.2)
Net income (loss)	24.7	5.2	31.5	14.0
Net income (loss) attributable to Ryerson Inc.	24.7	5.2	31.5	14.0
Comprehensive income (loss)	22.5	5.7	26.0	15.8
Comprehensive income (loss) attributable to Ryerson Inc.	22.5	5.7	26.0	15.8
Non-Guarantor [Member]
Schedule of Condensed Consolidating Statement of Comprehensive Income [Line Items]
Net sales	117.9	116.3	346.6	360.7
Cost of materials sold	98.7	99.0	290.9	309.6
Gross profit	19.2	17.3	55.7	51.1
Warehousing, delivery, selling, general and administrative	17.4	20.7	52.3	62.5
Restructuring and other charges				2.1
Gain on sale of assets	(1.3)		(1.3)
Impairment charges on fixed assets and goodwill				6.8
Operating profit (loss)	3.1	(3.4)	4.7	(20.3)
Other income and (expense), net	2.6	(1.1)	2.8	1.9
Interest and other expense on debt	(0.7)	(0.7)	(2.1)	(2.2)
Income (loss) before income taxes	5.0	(5.2)	5.4	(20.6)
Provision (benefit) for income taxes	(0.3)	(6.0)		(7.4)
Net income (loss)	5.3	0.8	5.4	(13.2)
Less: Net loss attributable to noncontrolling interest	(0.8)	(1.0)	(2.6)	(4.9)
Net income (loss) attributable to Ryerson Inc.	6.1	1.8	8.0	(8.3)
Comprehensive income (loss)	(3.8)	4.7	(3.9)	(19.1)
Less: Comprehensive loss attributable to noncontrolling interest	(0.8)	(1.2)	(2.7)	(4.9)
Comprehensive income (loss) attributable to Ryerson Inc.	(3.0)	5.9	(1.2)	(14.2)
Eliminations [Member]
Schedule of Condensed Consolidating Statement of Comprehensive Income [Line Items]
Net sales	(690.7)	(579.2)	(1,887.7)	(1,744.8)
Cost of materials sold	(690.7)	(579.2)	(1,887.7)	(1,744.8)
Interest expense on intercompany loans	6.9	7.4	21.9	19.4
Interest income on intercompany loans	(6.9)	(7.4)	(21.9)	(19.4)
Equity in (earnings) loss of subsidiaries	24.8	16.5	58.9	49.9
Net income (loss)	(24.8)	(16.5)	(58.9)	(49.9)
Net income (loss) attributable to Ryerson Inc.	(24.8)	(16.5)	(58.9)	(49.9)
Comprehensive income (loss)	(17.4)	(21.9)	(48.0)	(48.3)
Comprehensive income (loss) attributable to Ryerson Inc.	$ (17.4)	$ (21.9)	$ (48.0)	$ (48.3)