Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net sales	$ 814.5	$ 702.6
Cost of materials sold	653.9	555.0
Gross profit	160.6	147.6
Warehousing, delivery, selling, general and administrative	117.3	109.3
Operating profit	43.3	38.3
Other income and (expense), net	0.3	5.3
Interest and other expense on debt	(21.8)	(22.0)
Income before income taxes	21.8	21.6
Provision for income taxes	6.8	8.1
Net income	15.0	13.5
Less: Net income attributable to noncontrolling interest	0.2
Net income attributable to Ryerson Holding Corporation	14.8	13.5
Comprehensive income	16.3	21.9
Less: Comprehensive income attributable to noncontrolling interest	0.5
Comprehensive income attributable to Ryerson Holding Corporation	$ 15.8	$ 21.9
Basic and diluted earnings per share	$ 0.40	$ 0.42