EARNINGS PER SHARE (EPS) - Calculation of Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Net earnings
Net earnings	$ 90.4	$ 87.5
(Earnings) attributable to noncontrolling interest, net of tax	0.0	0.0
Net earnings attributable to Leggett & Platt, Inc. common shareholders	$ 90.4	$ 87.5
Weighted average number of shares (in millions):
Weighted average number of common shares used in basic EPS (in shares)	136.6	136.0
Dilutive effect of stock-based compensation (in shares)	0.3	0.3
Weighted average number of common shares and dilutive potential common shares used in diluted EPS (in shares)	136.9	136.3
Basic and diluted EPS:
Basic EPS attributable to Leggett & Platt, Inc. common shareholders (in dollars per share)	$ 0.66	$ 0.64
Diluted EPS attributable to Leggett & Platt, Inc. common shareholders (in dollars per share)	$ 0.66	$ 0.64
Other information:
Anti-dilutive shares excluded from diluted EPS computation (in shares)	0.4	0.2
Cash dividends declared per share (in usd per share)	$ 0.42	$ 0.40