Condensed Consolidating Financial Statements (Details 2) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Consolidating financial statements, captions
Net sales	$ 2,025.3	$ 2,288.3
Costs and expenses:
Cost of sales (exclusive of depreciation and amortization shown below)	1,496.5	1,710.5
Warehouse, delivery, selling, general and administrative	357.7	357.7
Depreciation and amortization	41.1	35.5
Total costs and expenses	1,895.3	2,103.7
Operating income	130.0	184.6
Other income (expense):
Interest	(13.1)	(14.5)
Other income (expense), net	2.9	6.5
(Loss) income before equity in earnings of subsidiaries and income taxes	119.8	176.6
Income before income taxes	119.8	176.6
Income tax (benefit) provision	35.3	58.7
Net income	84.5	117.9
Less: Net income attributable to noncontrolling interests	0.8	1.7
Net income attributable to Reliance	83.7	116.2
Parent
Consolidating financial statements, captions
Net sales	179.4	192.7
Costs and expenses:
Cost of sales (exclusive of depreciation and amortization shown below)	138.1	153.7
Warehouse, delivery, selling, general and administrative	50.9	15.0
Depreciation and amortization	4.0	3.5
Total costs and expenses	193.0	172.2
Operating income	(13.6)	20.5
Other income (expense):
Interest	(13.1)	(14.4)
Other income (expense), net	18.3	33.9
(Loss) income before equity in earnings of subsidiaries and income taxes	(8.4)	40.0
Equity in earnings of subsidiaries	82.6	68.0
Income before income taxes	74.2	108.0
Income tax (benefit) provision	(9.5)	(8.2)
Net income	83.7	116.2
Net income attributable to Reliance	83.7	116.2
Guarantor Subsidiaries
Consolidating financial statements, captions
Net sales	1,738.7	1,972.1
Costs and expenses:
Cost of sales (exclusive of depreciation and amortization shown below)	1,291.4	1,487.8
Warehouse, delivery, selling, general and administrative	299.6	344.4
Depreciation and amortization	33.6	29.2
Total costs and expenses	1,624.6	1,861.4
Operating income	114.1	110.7
Other income (expense):
Interest	(2.5)	(3.9)
Other income (expense), net	3.9	2.7
(Loss) income before equity in earnings of subsidiaries and income taxes	115.5	109.5
Equity in earnings of subsidiaries	4.8	9.9
Income before income taxes	120.3	119.4
Income tax (benefit) provision	42.2	62.2
Net income	78.1	57.2
Less: Net income attributable to noncontrolling interests	0.8	1.5
Net income attributable to Reliance	77.3	55.7
Non-Guarantor Subsidiaries
Consolidating financial statements, captions
Net sales	163.7	191.6
Costs and expenses:
Cost of sales (exclusive of depreciation and amortization shown below)	123.5	137.2
Warehouse, delivery, selling, general and administrative	23.3	24.8
Depreciation and amortization	3.5	2.8
Total costs and expenses	150.3	164.8
Operating income	13.4	26.8
Other income (expense):
Interest	(0.5)	(0.7)
Other income (expense), net	(0.2)	1.0
(Loss) income before equity in earnings of subsidiaries and income taxes	12.7	27.1
Income before income taxes	12.7	27.1
Income tax (benefit) provision	2.6	4.7
Net income	10.1	22.4
Less: Net income attributable to noncontrolling interests		0.2
Net income attributable to Reliance	10.1	22.2
Consolidating Adjustments
Consolidating financial statements, captions
Net sales	(56.5)	(68.1)
Costs and expenses:
Cost of sales (exclusive of depreciation and amortization shown below)	(56.5)	(68.2)
Warehouse, delivery, selling, general and administrative	(16.1)	(26.5)
Total costs and expenses	(72.6)	(94.7)
Operating income	16.1	26.6
Other income (expense):
Interest	3.0	4.5
Other income (expense), net	(19.1)	(31.1)
Equity in earnings of subsidiaries	(87.4)	(77.9)
Income before income taxes	(87.4)	(77.9)
Net income	(87.4)	(77.9)
Net income attributable to Reliance	$ (87.4)	$ (77.9)