Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Statement of Comprehensive Income [Abstract]
Net income	$ 146.4	$ 391.5	$ 295.4
Other comprehensive income (loss), before tax:
Foreign currency translation adjustments	4.7	(7.8)	(2.1)
Gain on cash flow hedges		1.9	2.1
Changes in defined benefit pension and other post-retirement benefit plans	(0.3)	38.6	142.4
Other comprehensive income, before tax	4.4	32.7	142.4
Income tax provision related to items of other comprehensive income		12.0	35.6
Comprehensive income, after tax	150.8	412.2	402.2
Less: Comprehensive income attributable to the noncontrolling interest	0.7	0.5	1.1
Comprehensive income attributable to Ryerson Holding Corporation	$ 150.1	$ 411.7	$ 401.1