Condensed Consolidating Guarantor Financial Statements - Condensed Consolidating Statement of Cash Flows (Unaudited) (Detail) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Operating activities:
Net income (loss)	$ 3.7	$ 5.1
Non-cash expenses	30.2	35.1
Changes in working capital	(24.5)	11.2
Net adjustments	5.7	46.3
Net cash provided by (used in) operating activities	9.4	51.4
Investing activities:
Capital expenditures	(8.2)	(10.5)
Other investing activities	1.1	3.1
Net cash provided by (used in) investing activities	(7.1)	(7.4)
Financing activities:
Net proceeds/(repayments) of short term borrowings	(40.0)	(36.8)
Net increase/(decrease) book overdrafts	47.5	6.1
Other financing activities	(0.5)	(4.3)
Net cash provided by (used in) financing activities	7.0	(35.0)
Net increase (decrease) in cash and cash equivalents	9.3	9.0
Effect of exchange rates	(0.8)	(4.1)
Net change in cash and cash equivalents	8.5	4.9
Cash and cash equivalents-beginning of period	74.0	70.8
Cash and cash equivalents-end of period	82.5	75.7
Parent [Member]
Operating activities:
Net income (loss)	5.5	9.0
Non-cash expenses	(9.0)	(0.1)
Equity in (earnings) loss of subsidiaries	(15.7)	(27.7)
Changes in working capital	3.8	629.4
Net adjustments	(20.9)	601.6
Net cash provided by (used in) operating activities	(15.4)	610.6
Investing activities:
Loan repayment from related companies		494.6
Other investing activities	(0.3)
Net cash provided by (used in) investing activities	(0.3)	494.6
Financing activities:
Net proceeds/(repayments) of short term borrowings	(44.1)	(38.6)
Proceeds from intercompany borrowings		399.7
Proceeds from intercompany borrowings	59.7	(1,458.3)
Net increase/(decrease) book overdrafts	0.2
Other financing activities		(3.2)
Net cash provided by (used in) financing activities	15.8	(1,100.4)
Net increase (decrease) in cash and cash equivalents	0.1	4.8
Net change in cash and cash equivalents	0.1	4.8
Cash and cash equivalents-beginning of period		0.2
Cash and cash equivalents-end of period	0.1	5.0
Joseph T. Ryerson [Member]
Operating activities:
Net income (loss)	25.4	34.7
Non-cash expenses	25.3	21.7
Equity in (earnings) loss of subsidiaries	(18.3)	(9.6)
Changes in working capital	13.6	1,021.7
Net adjustments	20.6	1,033.8
Net cash provided by (used in) operating activities	46.0	1,068.5
Investing activities:
Capital expenditures	(7.2)	(8.0)
Loan to related companies	(40.7)	(399.7)
Investment in related companies		(173.2)
Other investing activities	1.2	3.0
Net cash provided by (used in) investing activities	(46.7)	(577.9)
Financing activities:
Proceeds from intercompany borrowings		(494.6)
Net increase/(decrease) book overdrafts	2.2	(0.3)
Other financing activities	(0.5)	(0.6)
Net cash provided by (used in) financing activities	1.7	(495.5)
Net increase (decrease) in cash and cash equivalents	1.0	(4.9)
Effect of exchange rates		0.2
Net change in cash and cash equivalents	1.0	(4.7)
Cash and cash equivalents-beginning of period	7.8	15.3
Cash and cash equivalents-end of period	8.8	10.6
Guarantor [Member]
Operating activities:
Net income (loss)	6.8	8.8
Non-cash expenses	9.1	1.5
Equity in (earnings) loss of subsidiaries	(0.1)	3.9
Changes in working capital	(25.5)	(1,650.6)
Net adjustments	(16.5)	(1,645.2)
Net cash provided by (used in) operating activities	(9.7)	(1,636.4)
Investing activities:
Capital expenditures	(0.4)	(0.3)
Loan to related companies	(19.0)
Loan repayment from related companies		1,458.3
Net cash provided by (used in) investing activities	(19.4)	1,458.0
Financing activities:
Net increase/(decrease) book overdrafts	45.1	6.4
Capital contribution		173.2
Net cash provided by (used in) financing activities	45.1	179.6
Net increase (decrease) in cash and cash equivalents	16.0	1.2
Net change in cash and cash equivalents	16.0	1.2
Cash and cash equivalents-beginning of period	2.4	1.9
Cash and cash equivalents-end of period	18.4	3.1
Non-Guarantor [Member]
Operating activities:
Net income (loss)	0.1	(14.0)
Non-cash expenses	3.3	12.0
Changes in working capital	(14.9)	10.7
Net adjustments	(11.6)	22.7
Net cash provided by (used in) operating activities	(11.5)	8.7
Investing activities:
Capital expenditures	(0.6)	(2.2)
Other investing activities	0.1	0.1
Net cash provided by (used in) investing activities	(0.5)	(2.1)
Financing activities:
Net proceeds/(repayments) of short term borrowings	4.1	1.8
Other financing activities	0.1	(0.5)
Net cash provided by (used in) financing activities	4.2	1.3
Net increase (decrease) in cash and cash equivalents	(7.8)	7.9
Effect of exchange rates	(0.8)	(4.3)
Net change in cash and cash equivalents	(8.6)	3.6
Cash and cash equivalents-beginning of period	63.8	53.4
Cash and cash equivalents-end of period	55.2	57.0
Eliminations [Member]
Operating activities:
Net income (loss)	(34.1)	(33.4)
Non-cash expenses	1.5
Equity in (earnings) loss of subsidiaries	34.1	33.4
Changes in working capital	(1.5)
Net adjustments	34.1	33.4
Investing activities:
Loan to related companies	59.7	399.7
Loan repayment from related companies		(1,952.9)
Investment in related companies		173.2
Other investing activities	0.1
Net cash provided by (used in) investing activities	59.8	(1,380.0)
Financing activities:
Proceeds from intercompany borrowings		(399.7)
Proceeds from intercompany borrowings	(59.7)	1,952.9
Capital contribution		(173.2)
Other financing activities	(0.1)
Net cash provided by (used in) financing activities	$ (59.8)	$ 1,380.0