Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net sales	$ 1,010.3	$ 1,230.8
Cost of materials sold	814.5	999.5
Gross profit	195.8	231.3
Warehousing, delivery, selling, general, and administrative	155.7	163.7
Restructuring and other charges		0.3
Operating profit	40.1	67.3
Other income and (expense), net	0.9	(0.8)
Interest and other expense on debt	(21.7)	(23.9)
Income before income taxes	19.3	42.6
Provision for income taxes	2.9	13.0
Net income	16.4	29.6
Less: Net income attributable to noncontrolling interest		0.1
Net income attributable to Ryerson Holding Corporation	16.4	29.5
Comprehensive income	6.2	33.1
Less: Comprehensive income attributable to noncontrolling interest		0.2
Comprehensive income attributable to Ryerson Holding Corporation	$ 6.2	$ 32.9
Basic earnings per share	$ 0.43	$ 0.79
Diluted earnings per share	$ 0.43	$ 0.78