Condensed Consolidating Guarantor Financial Statements - Condensed Consolidating Statement of Cash Flows (Unaudited) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013
Operating activities:
Net income (loss)	$ (22.7)	$ 8.4
Non-cash expenses	34.7	53.3
Changes in working capital	(56.6)	26.3
Net adjustments	(21.9)	79.6
Net cash provided by (used in) operating activities	(44.6)	88.0
Investing activities:
Capital expenditures	(13.7)	(16.5)
Other investing activities	3.8	3.6
Net cash provided by (used in) investing activities	(9.9)	(12.9)
Financing activities:
Repayment of debt	(110.7)
Net proceeds/(repayments) of short-term borrowings	32.5	(65.3)
Net increase book overdrafts	21.8	7.7
Capital contribution	110.7
Other financing activities	(0.7)	2.8
Net cash provided by (used in) financing activities	53.6	(62.5)
Net increase (decrease) in cash and cash equivalents	(0.9)	12.6
Effect of exchange rates	(4.5)	(2.7)
Net change in cash and cash equivalents	(5.4)	9.9
Cash and cash equivalents-beginning of period	74.0	70.8
Cash and cash equivalents-end of period	68.6	80.7
Parent [Member]
Operating activities:
Net income (loss)	(20.1)	13.3
Non-cash expenses	4.2	(0.1)
Equity in (earnings) loss of subsidiaries	(25.5)	(35.4)
Changes in working capital	16.3	616.5
Net adjustments	(5.0)	581.0
Net cash provided by (used in) operating activities	(25.1)	594.3
Investing activities:
Loan repayment from related parties		494.6
Other investing activities	(0.3)	(0.9)
Net cash provided by (used in) investing activities	(0.3)	493.7
Financing activities:
Net proceeds/(repayments) of short-term borrowings	28.5	(65.0)
Proceeds from intercompany borrowings	16.4	432.4
Repayment of intercompany borrowings	(129.9)	(1,444.7)
Net increase book overdrafts	0.2
Capital contribution	110.7
Other financing activities		(3.2)
Net cash provided by (used in) financing activities	25.9	(1,080.5)
Net increase (decrease) in cash and cash equivalents	0.5	7.5
Net change in cash and cash equivalents	0.5	7.5
Cash and cash equivalents-beginning of period		0.2
Cash and cash equivalents-end of period	0.5	7.7
Joseph T. Ryerson [Member]
Operating activities:
Net income (loss)	19.4	44.2
Non-cash expenses	21.5	37.8
Equity in (earnings) loss of subsidiaries	(31.4)	(14.3)
Changes in working capital	(15.7)	1,038.0
Net adjustments	(25.6)	1,061.5
Net cash provided by (used in) operating activities	(6.2)	1,105.7
Investing activities:
Capital expenditures	(12.2)	(13.2)
Loan to related companies		(432.4)
Loan repayment from related parties	129.9
Investment in related companies		(173.2)
Other investing activities	1.3	4.3
Net cash provided by (used in) investing activities	119.0	(614.5)
Financing activities:
Repayment of debt	(110.7)
Repayment of intercompany borrowings		(494.6)
Net increase book overdrafts	1.3
Other financing activities	(0.7)	(1.3)
Net cash provided by (used in) financing activities	(110.1)	(495.9)
Net increase (decrease) in cash and cash equivalents	2.7	(4.7)
Net change in cash and cash equivalents	2.7	(4.7)
Cash and cash equivalents-beginning of period	7.8	15.3
Cash and cash equivalents-end of period	10.5	10.6
Guarantor [Member]
Operating activities:
Net income (loss)	31.5	14.0
Non-cash expenses	3.2	2.5
Equity in (earnings) loss of subsidiaries	(2.0)	(0.2)
Changes in working capital	(37.4)	(1,640.1)
Net adjustments	(36.2)	(1,637.8)
Net cash provided by (used in) operating activities	(4.7)	(1,623.8)
Investing activities:
Capital expenditures	(0.3)	(0.5)
Loan to related companies	(16.4)
Loan repayment from related parties		1,444.7
Net cash provided by (used in) investing activities	(16.7)	1,444.2
Financing activities:
Net increase book overdrafts	20.3
Capital contribution		173.2
Other financing activities		7.8
Net cash provided by (used in) financing activities	20.3	181.0
Net increase (decrease) in cash and cash equivalents	(1.1)	1.4
Effect of exchange rates	0.1	(0.1)
Net change in cash and cash equivalents	(1.0)	1.3
Cash and cash equivalents-beginning of period	2.4	1.9
Cash and cash equivalents-end of period	1.4	3.2
Non-Guarantor [Member]
Operating activities:
Net income (loss)	5.4	(13.2)
Non-cash expenses	4.3	13.1
Changes in working capital	(18.3)	11.9
Net adjustments	(14.0)	25.0
Net cash provided by (used in) operating activities	(8.6)	11.8
Investing activities:
Capital expenditures	(1.2)	(2.8)
Other investing activities	2.7	0.2
Net cash provided by (used in) investing activities	1.5	(2.6)
Financing activities:
Net proceeds/(repayments) of short-term borrowings	4.0	(0.3)
Capital contribution	0.1
Other financing activities		(0.5)
Net cash provided by (used in) financing activities	4.1	(0.8)
Net increase (decrease) in cash and cash equivalents	(3.0)	8.4
Effect of exchange rates	(4.6)	(2.6)
Net change in cash and cash equivalents	(7.6)	5.8
Cash and cash equivalents-beginning of period	63.8	53.4
Cash and cash equivalents-end of period	56.2	59.2
Eliminations [Member]
Operating activities:
Net income (loss)	(58.9)	(49.9)
Non-cash expenses	1.5
Equity in (earnings) loss of subsidiaries	58.9	49.9
Changes in working capital	(1.5)
Net adjustments	58.9	49.9
Investing activities:
Loan to related companies	16.4	432.4
Loan repayment from related parties	(129.9)	(1,939.3)
Investment in related companies		173.2
Other investing activities	0.1
Net cash provided by (used in) investing activities	(113.4)	(1,333.7)
Financing activities:
Proceeds from intercompany borrowings	(16.4)	(432.4)
Repayment of intercompany borrowings	129.9	1,939.3
Capital contribution	(0.1)	(173.2)
Net cash provided by (used in) financing activities	$ 113.4	$ 1,333.7