CONSOLIDATED CONDENSED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Income Statement [Abstract]
Net trade sales	$ 1,319,200,000	$ 1,207,600,000	$ 3,739,700,000	$ 3,098,200,000
Cost of goods sold	1,063,100,000	937,900,000	2,966,800,000	2,461,200,000
Gross profit	256,100,000	269,700,000	772,900,000	637,000,000.0
Selling and administrative expenses	103,600,000	105,600,000	322,500,000	320,600,000
Amortization of intangibles	17,800,000	16,200,000	51,600,000	48,900,000
Impairments	0	0	0	29,400,000
Net gain from sale of assets and businesses	900,000	2,100,000	29,500,000	2,100,000
Other (income) expense, net	(8,600,000)	(200,000)	(15,500,000)	(11,300,000)
Earnings before interest and income taxes	144,200,000	150,200,000	443,800,000	251,500,000
Interest expense	19,000,000.0	20,900,000	57,800,000	63,200,000
Interest income	600,000	500,000	2,300,000	2,400,000
Earnings before income taxes	125,800,000	129,800,000	388,300,000	190,700,000
Income taxes	28,600,000	22,700,000	91,300,000	45,600,000
Net earnings	97,200,000	107,100,000	297,000,000.0	145,100,000
(Earnings) attributable to noncontrolling interest, net of tax	0	(100,000)	(100,000)	(100,000)
Net earnings attributable to Leggett & Platt, Inc. common shareholders	$ 97,200,000	$ 107,000,000.0	$ 296,900,000	$ 145,000,000.0
Net earnings per share attributable to Leggett & Platt, Inc. common shareholders
Basic (in dollars per share)	$ 0.71	$ 0.79	$ 2.18	$ 1.07
Diluted (in dollars per share)	$ 0.71	$ 0.79	$ 2.17	$ 1.07
Weighted average shares outstanding
Basic (in shares)	136.4	135.8	136.2	135.6
Diluted (in shares)	136.9	136.1	136.7	135.8