Condensed Consolidating Guarantor Financial Statements - Condensed Consolidating Balance Sheet (Unaudited) (Detail) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
ASSETS
Cash and cash equivalents	$ 68.6	$ 74.0	$ 80.7	$ 70.8
Receivables less provision for allowances, claims and doubtful accounts	468.2	385.4
Inventories	736.0	733.0
Other current assets	39.0	49.5
Total current assets	1,311.8	1,241.9
Property, plant and equipment net of accumulated depreciation	433.9	452.7
Other noncurrent assets	221.5	223.4
Total assets	1,967.2	1,918.0
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	286.0	207.2
Deferred income taxes	117.7	121.0
Other current liabilities	158.2	132.9
Total current liabilities	561.9	461.1
Long-term debt	1,198.1	1,262.5
Deferred employee benefits	253.7	320.8
Taxes and other credits	19.7	16.8
Total liabilities	2,033.4	2,061.2
Redeemable noncontrolling interest	1.2	1.3
Ryerson Inc. stockholders' equity	(62.3)	(142.0)
Noncontrolling interest	(5.1)	(2.5)
Total liabilities and equity	1,967.2	1,918.0
Parent [Member]
ASSETS
Cash and cash equivalents	0.5		7.7	0.2
Receivables less provision for allowances, claims and doubtful accounts	1.0	3.5
Other current assets	0.2
Total current assets	1.7	3.5
Investments in subsidiaries	1,020.2	1,005.7
Other noncurrent assets	101.1	107.3
Total assets	1,123.0	1,116.5
LIABILITIES AND STOCKHOLDERS' EQUITY
Intercompany payable	261.2	247.6
Deferred income taxes	1.3	2.9
Other current liabilities	2.9	8.8
Total current liabilities	265.4	259.3
Long-term debt	397.6	362.5
Long-term debt - intercompany	516.4	629.9
Deferred employee benefits	0.7	0.6
Taxes and other credits	5.2	6.2
Total liabilities	1,185.3	1,258.5
Ryerson Inc. stockholders' equity	(62.3)	(142.0)
Total liabilities and equity	1,123.0	1,116.5
Joseph T. Ryerson [Member]
ASSETS
Cash and cash equivalents	10.5	7.8	10.6	15.3
Receivables less provision for allowances, claims and doubtful accounts	366.8	290.4
Inventories	632.8	637.1
Intercompany receivable	157.0	227.0
Other current assets	10.0	11.4
Total current assets	1,177.1	1,173.7
Investments in subsidiaries	447.4	416.0
Intercompany notes receivable	276.2	406.1
Property, plant and equipment net of accumulated depreciation	373.4	387.8
Other noncurrent assets	57.0	48.5
Total assets	2,331.1	2,432.1
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	45.9	35.1
Deferred income taxes	119.1	119.1
Other current liabilities	109.2	85.5
Total current liabilities	274.2	239.7
Long-term debt	800.5	900.0
Deferred employee benefits	229.8	294.4
Taxes and other credits	11.1	5.6
Total liabilities	1,315.6	1,439.7
Ryerson Inc. stockholders' equity	1,015.5	992.4
Total liabilities and equity	2,331.1	2,432.1
Guarantor [Member]
ASSETS
Cash and cash equivalents	1.4	2.4	3.2	1.9
Receivables less provision for allowances, claims and doubtful accounts	13.2	8.8
Inventories	27.1	25.8
Intercompany receivable	137.6	55.2
Other current assets	12.0	20.8
Total current assets	191.3	113.0
Investments in subsidiaries	36.1	34.0
Intercompany notes receivable	240.2	223.8
Property, plant and equipment net of accumulated depreciation	3.3	3.1
Other noncurrent assets	61.7	64.0
Total assets	532.6	437.9
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	201.6	132.8
Deferred income taxes	0.5	0.5
Other current liabilities	4.3	1.7
Total current liabilities	206.4	135.0
Taxes and other credits	2.6	5.3
Total liabilities	209.0	140.3
Ryerson Inc. stockholders' equity	323.6	297.6
Total liabilities and equity	532.6	437.9
Non-Guarantor [Member]
ASSETS
Cash and cash equivalents	56.2	63.8	59.2	53.4
Receivables less provision for allowances, claims and doubtful accounts	87.2	82.7
Inventories	76.1	70.1
Other current assets	17.8	18.8
Total current assets	237.3	235.4
Property, plant and equipment net of accumulated depreciation	57.2	61.8
Other noncurrent assets	5.1	5.8
Total assets	299.6	303.0
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	38.6	39.1
Intercompany payable	33.3	35.0
Other current liabilities	41.8	36.7
Total current liabilities	113.7	110.8
Deferred employee benefits	23.2	25.8
Taxes and other credits	2.0	1.9
Total liabilities	138.9	138.5
Redeemable noncontrolling interest	1.2	1.3
Ryerson Inc. stockholders' equity	164.6	165.7
Noncontrolling interest	(5.1)	(2.5)
Total liabilities and equity	299.6	303.0
Eliminations [Member]
ASSETS
Intercompany receivable	(294.6)	(282.2)
Other current assets	(1.0)	(1.5)
Total current assets	(295.6)	(283.7)
Investments in subsidiaries	(1,503.7)	(1,455.7)
Intercompany notes receivable	(516.4)	(629.9)
Other noncurrent assets	(3.4)	(2.2)
Total assets	(2,319.1)	(2,371.5)
LIABILITIES AND STOCKHOLDERS' EQUITY
Accounts payable	(0.1)	0.2
Intercompany payable	(294.5)	(282.6)
Deferred income taxes	(3.2)	(1.5)
Other current liabilities		0.2
Total current liabilities	(297.8)	(283.7)
Long-term debt - intercompany	(516.4)	(629.9)
Taxes and other credits	(1.2)	(2.2)
Total liabilities	(815.4)	(915.8)
Ryerson Inc. stockholders' equity	(1,503.7)	(1,455.7)
Total liabilities and equity	$ (2,319.1)	$ (2,371.5)