EARNINGS PER SHARE - Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Net earnings:
Net earnings	$ 45.7	$ 61.1
Loss attributable to noncontrolling interest, net of tax	0.0	0.1
Net earnings attributable to Leggett & Platt, Inc. common shareholders	$ 45.7	$ 61.2
Weighted average number of shares:
Weighted average number of common shares used in basic EPS (in shares)	135,400	134,400
Dilutive effect of stock-based compensation (in shares)	200	600
Weighted average number of common shares and dilutive potential common shares used in diluted EPS (in shares)	135,600	135,000
Basic and Diluted EPS:
Basic EPS attributable to Leggett & Platt, Inc. common shareholders (in dollars per share)	$ 0.34	$ 0.46
Diluted EPS attributable to Leggett & Platt, Inc. common shareholders (in dollars per share)	$ 0.34	$ 0.45
Other information:
Anti-dilutive shares excluded from diluted EPS computation (in shares)	200	100
Cash dividends declared per share (in dollars per share)	$ 0.40	$ 0.38