Equity - Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Schedule of accumulated other comprehensive loss
Balance at the beginning of the year	$ (86.3)
Current-period change	9.6
Balance at the end of the year	(76.7)	$ (86.3)
Deferred tax assets in accumulated other comprehensive loss, pension liabilities	0.7	1.3
Income tax portion attributable to settlement of Reliance SERP		0.3
Foreign Currency Translation (Loss) Gain
Schedule of accumulated other comprehensive loss
Balance at the beginning of the year	(84.0)
Current-period change	8.3
Balance at the end of the year	(75.7)	(84.0)
Pension and Postretirement Benefit Plan Adjustments, Net of Tax
Schedule of accumulated other comprehensive loss
Balance at the beginning of the year	(2.3)
Current-period change	1.3
Balance at the end of the year	$ (1.0)	$ (2.3)