Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net income attributable to Reliance	$ 1,840.1	$ 1,413.0	$ 369.1
Denominator:
Weighted average shares outstanding (in shares)	60,559,000	63,217,000	64,328,000
Dilutive effect of stock-based awards (in shares)	936,000	1,110,000	935,000
Weighted average diluted shares outstanding (in shares)	61,495,000	64,327,000	65,263,000
Earnings per share attributable to Reliance stockholders - basic (in dollars per share)	$ 30.39	$ 22.35	$ 5.74
Earnings per share attributable to Reliance stockholders - diluted (in dollars per share)	$ 29.92	$ 21.97	$ 5.66
Diluted shares
Weighted average shares, respectively, for RSU's, not included in the diluted calculation due to their anti-dilutive effect	83,857	116,206	183,508