UNAUDITED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Millions	Reliance Stockholders'	Common Stock and Additional Paid in Capital	Retained Earnings	Accumulated Other Comprehensive Loss	Non-controlling Interests	Total
Balances at Dec. 31, 2022		$ 0.1	$ 7,173.6	$ (86.3)	$ 8.5	$ 7,095.9
Increase (Decrease) in Stockholders' Equity
Net income attributable to Reliance			1,063.2			1,063.2
Cash dividends and dividend equivalents			(179.3)
Other comprehensive income (loss)				(13.1)		(13.1)
Comprehensive income					3.5	(3.5)
Dividends paid					(1.1)
Stock-based compensation		48.4
Taxes paid related to net share settlement of restricted stock units		(11.5)	(29.8)
Repurchase of common shares		(36.9)	(202.3)
Excise tax on repurchase of common shares			(1.8)
Balances at Sep. 30, 2023	$ 7,724.3	0.1	7,823.6	(99.4)	10.9	7,735.2
Balances at Jun. 30, 2023		0.1	7,702.1	(86.6)	9.9	7,625.5
Increase (Decrease) in Stockholders' Equity
Net income attributable to Reliance			295.0			295.0
Cash dividends and dividend equivalents			(58.7)
Other comprehensive income (loss)				(12.8)		(12.8)
Comprehensive income					1.0	(1.0)
Stock-based compensation		16.8
Taxes paid related to net share settlement of restricted stock units		(4.0)
Repurchase of common shares		(12.8)	(113.6)
Excise tax on repurchase of common shares			(1.2)
Balances at Sep. 30, 2023	7,724.3	0.1	7,823.6	(99.4)	10.9	7,735.2
Balances at Dec. 31, 2023		0.1	7,798.9	(76.7)	10.5	7,732.8
Increase (Decrease) in Stockholders' Equity
Net income attributable to Reliance			769.9			769.9
Cash dividends and dividend equivalents			(188.5)
Other comprehensive income (loss)				(6.4)		(6.4)
Comprehensive income					2.1	(2.1)
Acquisition					0.3
Dividends paid					(2.2)
Stock-based compensation		43.0
Taxes paid related to net share settlement of restricted stock units		(18.5)	(11.1)
Repurchase of common shares		(24.5)	(926.8)
Excise tax on repurchase of common shares			(8.9)
Balances at Sep. 30, 2024	7,350.5	0.1	7,433.5	(83.1)	10.7	7,361.2
Balances at Jun. 30, 2024		0.1	7,724.4	(101.5)	10.0	7,633.0
Increase (Decrease) in Stockholders' Equity
Net income attributable to Reliance			199.2			199.2
Cash dividends and dividend equivalents			(60.6)
Other comprehensive income (loss)				18.4		18.4
Comprehensive income					0.7	(0.7)
Stock-based compensation		16.1
Taxes paid related to net share settlement of restricted stock units		(5.3)	(0.2)
Repurchase of common shares		(10.8)	(421.2)
Excise tax on repurchase of common shares			(8.1)
Balances at Sep. 30, 2024	$ 7,350.5	$ 0.1	$ 7,433.5	$ (83.1)	$ 10.7	$ 7,361.2