Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 295.4	$ (65.3)	$ 82.7
Other comprehensive income (loss), before tax:
Foreign currency translation adjustments	(2.1)	1.6	4.3
Gain (loss) on hedges	2.1	(3.8)	(1.8)
Changes in defined benefit pension and other post-retirement benefit plans	142.4	41.8	14.0
Other comprehensive income, before tax	142.4	39.6	16.5
Income tax provision related to items of other comprehensive income	35.6	9.5	2.6
Comprehensive income (loss), after tax	402.2	(35.2)	96.6
Less: Comprehensive income attributable to the noncontrolling interest	1.1	0.5	0.4
Comprehensive income (loss) attributable to Ryerson Holding Corporation	$ 401.1	$ (35.7)	$ 96.2