Condensed Consolidating Guarantor Financial Statements - Condensed Consolidating Statement of Cash Flows (Unaudited) (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Operating activities:
Net income (loss)	$ 1.0	$ 4.9
Non-cash expenses	17.1	13.9
Changes in working capital	6.9	10.9
Net adjustments	24.0	24.8
Net cash provided by (used in) operating activities	25.0	29.7
Investing activities:
Net cash provided by (used in) investing activities	(3.3)	(3.9)
Financing activities:
Net cash provided by (used in) financing activities	5.0	(21.4)
Net increase in cash and cash equivalents	26.7	4.4
Effect of exchange rates	(3.7)	(1.2)
Net change in cash and cash equivalents	23.0	3.2
Cash and cash equivalents-beginning of period	74.0	70.8
Cash and cash equivalents-end of period	97.0	74.0
Parent [Member]
Operating activities:
Net income (loss)	1.9	7.1
Non-cash expenses	(8.5)	0.1
Equity in (earnings) loss of subsidiaries	(4.5)	(16.7)
Changes in working capital	0.4	625.2
Net adjustments	(12.6)	608.6
Net cash provided by (used in) operating activities	(10.7)	615.7
Investing activities:
Net cash provided by (used in) investing activities		(0.1)
Financing activities:
Net cash provided by (used in) financing activities	31.6	(615.2)
Net increase in cash and cash equivalents	20.9	0.4
Net change in cash and cash equivalents	20.9	0.4
Cash and cash equivalents-beginning of period		0.2
Cash and cash equivalents-end of period	20.9	0.6
Joseph T. Ryerson [Member]
Operating activities:
Net income (loss)	11.4	18.9
Non-cash expenses	15.5	11.4
Equity in (earnings) loss of subsidiaries	(9.7)	(8.0)
Changes in working capital	(67.1)	1,044.6
Net adjustments	(61.3)	1,048.0
Net cash provided by (used in) operating activities	(49.9)	1,066.9
Investing activities:
Net cash provided by (used in) investing activities	41.7	(577.8)
Financing activities:
Net cash provided by (used in) financing activities	12.0	(492.9)
Net increase in cash and cash equivalents	3.8	(3.8)
Effect of exchange rates		0.2
Net change in cash and cash equivalents	3.8	(3.6)
Cash and cash equivalents-beginning of period	7.8	15.3
Cash and cash equivalents-end of period	11.6	11.7
Guarantor [Member]
Operating activities:
Net income (loss)	0.9	5.8
Non-cash expenses	6.9	0.9
Equity in (earnings) loss of subsidiaries	1.2	0.9
Changes in working capital	85.0	(1,662.4)
Net adjustments	93.1	(1,660.6)
Net cash provided by (used in) operating activities	94.0	(1,654.8)
Investing activities:
Net cash provided by (used in) investing activities	(103.0)	1,464.3
Financing activities:
Net cash provided by (used in) financing activities	12.8	191.2
Net increase in cash and cash equivalents	3.8	0.7
Effect of exchange rates		(0.1)
Net change in cash and cash equivalents	3.8	0.6
Cash and cash equivalents-beginning of period	2.4	1.9
Cash and cash equivalents-end of period	6.2	2.5
Non-Guarantor [Member]
Operating activities:
Net income (loss)	(0.2)	(3.1)
Non-cash expenses	1.7	1.5
Changes in working capital	(9.9)	3.5
Net adjustments	(8.2)	5.0
Net cash provided by (used in) operating activities	(8.4)	1.9
Investing activities:
Net cash provided by (used in) investing activities	(0.2)	(0.9)
Financing activities:
Net cash provided by (used in) financing activities	6.8	6.1
Net increase in cash and cash equivalents	(1.8)	7.1
Effect of exchange rates	(3.7)	(1.3)
Net change in cash and cash equivalents	(5.5)	5.8
Cash and cash equivalents-beginning of period	63.8	53.4
Cash and cash equivalents-end of period	58.3	59.2
Eliminations [Member]
Operating activities:
Net income (loss)	(13.0)	(23.8)
Non-cash expenses	1.5
Equity in (earnings) loss of subsidiaries	13.0	23.8
Changes in working capital	(1.5)
Net adjustments	13.0	23.8
Investing activities:
Net cash provided by (used in) investing activities	58.2	(889.4)
Financing activities:
Net cash provided by (used in) financing activities	$ (58.2)	$ 889.4