EARNINGS PER SHARE - Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net earnings:
Net earnings	$ 61.1	$ 77.9
Loss attributable to noncontrolling interest, net of tax	0.1	0.0
Net earnings attributable to Leggett & Platt, Inc. common shareholders	$ 61.2	$ 77.9
Weighted average number of shares:
Weighted average number of common shares used in basic EPS (in shares)	134.4	135.3
Dilutive effect of stock-based compensation (in shares)	0.6	1.0
Weighted average number of common shares and dilutive potential common shares used in diluted EPS (in shares)	135.0	136.3
Basic and Diluted EPS:
Basic EPS attributable to Leggett & Platt, Inc. common shareholders (in dollars per share)	$ 0.46	$ 0.58
Diluted EPS attributable to Leggett & Platt, Inc. common shareholders (in dollars per share)	$ 0.45	$ 0.57
Other information:
Anti-dilutive shares excluded from diluted EPS computation (in shares)	0.1	0.1
Cash dividends declared per share (in dollars per share)	$ 0.38	$ 0.36