Condensed Consolidating Financial Statements (Details) (USD $) In Millions, unless otherwise specified					1 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Nov. 30, 2006 Senior Unsecured Notes - Publicly Traded	Dec. 31, 2012 Parent	Dec. 31, 2011 Parent	Dec. 31, 2010 Parent	Dec. 31, 2009 Parent	Dec. 31, 2012 Guarantor Subsidiaries	Dec. 31, 2011 Guarantor Subsidiaries	Dec. 31, 2010 Guarantor Subsidiaries	Dec. 31, 2009 Guarantor Subsidiaries	Dec. 31, 2012 Non-Guarantor Subsidiaries	Dec. 31, 2011 Non-Guarantor Subsidiaries	Dec. 31, 2010 Non-Guarantor Subsidiaries	Dec. 31, 2009 Non-Guarantor Subsidiaries	Dec. 31, 2012 Eliminations & Reclassifications	Dec. 31, 2011 Eliminations & Reclassifications
Consolidating financial statements, captions
Aggregate principal amount					$ 600
Ownership interest in domestic subsidiaries (as a percent)	100.00%				100.00%
ASSETS
Cash and cash equivalents	97.6	84.6	72.9	43.0		28.1	15.1	14.4	9.0	13.1	10.8	8.0	6.9	56.4	58.7	50.5	27.1
Accounts receivable, less allowance for doubtful accounts	807.7	896.2				67.4	69.6			658.3	739.1			82.0	87.5
Inventories	1,272.3	1,212.8				50.3	43.7			1,068.4	1,017.4			153.6	151.7
Intercompany receivables						0.2	0.3			16.7	11.6			2.4	0.9			(19.3)	(12.8)
Income taxes receivable	28.4					28.2								0.2
Other current assets	71.4	81.1				113.3	108.7			26.5	28.0			6.8	7.5			(75.2)	(63.1)
Total current assets	2,277.4	2,274.7				287.5	237.4			1,783.0	1,806.9			301.4	306.3			(94.5)	(75.9)
Investments in subsidiaries						3,722.7	3,217.0			257.8	273.9							(3,980.5)	(3,490.9)
Property, plant and equipment, net	1,240.7	1,105.5				100.8	100.0			1,044.1	931.5			95.8	74.0
Goodwill	1,314.6	1,244.3	1,109.6	1,081.3		23.7	23.8			1,183.9	1,115.7			107.0	104.8
Intangible assets, net	936.5	895.9				11.0	13.6			794.6	748.0			130.9	134.3
Intercompany receivables						969.7	1,229.9			26.2	35.9			3.7				(999.6)	(1,265.8)
Other assets	88.5	85.5				18.3	13.7			68.1	70.0			2.1	1.8
Total assets	5,857.7	5,605.9				5,133.7	4,835.4			5,157.7	4,981.9			640.9	621.2			(5,074.6)	(4,832.6)
Liabilities & Equity
Accounts payable	255.6	335.2				25.7	31.2			195.2	270.6			54.0	46.2			(19.3)	(12.8)
Accrued compensation and retirement costs	112.8	111.0				22.8	22.0			84.0	81.4			6.0	7.6
Other current liabilities	126.2	118.0				48.5	49.3			71.6	41.4			6.1	15.4				11.9
Deferred income taxes										75.2	75.0							(75.2)	(75.0)
Current maturities of long-term debt and short-term borrowings	83.6	12.2				75.3	0.2				0.2			8.3	11.8
Total current liabilities	578.2	576.4				172.3	102.7			426.0	468.6			74.4	81.0			(94.5)	(75.9)
Long-term debt	1,123.8	1,319.0				1,123.8	1,319.0
Intercompany borrowings										864.3	1,097.2			135.3	168.6			(999.6)	(1,265.8)
Other long-term liabilities	588.3	558.5				279.2	269.8			284.0	264.9			25.1	23.8
Total Reliance shareholders' equity	3,558.4	3,143.9				3,558.4	3,143.9			3,577.4	3,146.8			403.1	344.1			(3,980.5)	(3,490.9)
Noncontrolling interests	9.0	8.1								6.0	4.4			3.0	3.7
Total equity	3,567.4	3,152.0	2,830.1	2,608.1		3,558.4	3,143.9			3,583.4	3,151.2			406.1	347.8			(3,980.5)	(3,490.9)
Total liabilities and equity	$ 5,857.7	$ 5,605.9				$ 5,133.7	$ 4,835.4			$ 5,157.7	$ 4,981.9			$ 640.9	$ 621.2			$ (5,074.6)	$ (4,832.6)