Consolidated Statement Of Changes In Equity - USD ($) shares in Millions, $ in Millions	Total	Common Stock	Additional Contributed Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjusted beginning balance	$ 1,095.1	$ 2.0	$ 506.2	$ 2,411.6	$ (113.6)	$ (1,713.5)	$ 2.4
Balance, beginning of period at Dec. 31, 2016	1,094.0	$ 2.0	506.2	2,410.5	(113.6)	$ (1,713.5)	2.4
Balance, beginning of period, (in shares) at Dec. 31, 2016		198.8				(65.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings attributable to Leggett & Platt, Inc. common shareholders	292.7			292.6			0.1
Dividends declared	(187.7)		5.2	(192.9)
Treasury stock purchased	(162.1)					$ (162.1)
Treasury stock purchased, (in shares)						(3.3)
Treasury stock issued	31.2		(16.1)			$ 47.3
Treasury stock issued, (in shares)						1.7
Other comprehensive income (loss), net of tax (See Note Q)	103.7				103.7
Stock-based compensation, net of tax	20.0		20.0
Purchase of remaining interest in noncontrolling interest	(2.6)		(0.6)		0.4		(2.4)
Acquisition of noncontrolling interest	0.5						0.5
Balance, end of period at Dec. 31, 2017	1,190.8	$ 2.0	514.7	2,511.3	(9.5)	$ (1,828.3)	0.6
Balance, end of period, (in shares) at Dec. 31, 2017		198.8				(66.9)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjusted beginning balance	1,188.5	$ 2.0	514.7	2,509.0	(9.5)	$ (1,828.3)	0.6
Net earnings attributable to Leggett & Platt, Inc. common shareholders	306.1			305.9			0.2
Dividends declared	(195.8)		5.3	(201.1)
Dividends paid to noncontrolling interest	(0.2)						(0.2)
Treasury stock purchased	(113.6)					$ (113.6)
Treasury stock purchased, (in shares)						(2.6)
Treasury stock issued	17.0		(16.6)			$ 33.6
Treasury stock issued, (in shares)						1.2
Other comprehensive income (loss), net of tax (See Note Q)	(68.1)				(68.1)
Stock-based compensation, net of tax	23.7		23.7
Balance, end of period at Dec. 31, 2018	1,157.6	$ 2.0	527.1	2,613.8	(77.6)	$ (1,908.3)	0.6
Balance, end of period, (in shares) at Dec. 31, 2018		198.8				(68.3)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjusted beginning balance	1,157.7	$ 2.0	527.1	2,613.9	(77.6)	$ (1,908.3)	0.6
Net earnings attributable to Leggett & Platt, Inc. common shareholders	333.9			333.8			0.1
Dividends declared	(207.8)		5.4	(213.2)
Dividends paid to noncontrolling interest	(0.2)						(0.2)
Treasury stock purchased	(31.1)					$ (31.1)
Treasury stock purchased, (in shares)						(0.7)
Treasury stock issued	33.3		(22.3)			$ 55.6
Treasury stock issued, (in shares)						2.0
Other comprehensive income (loss), net of tax (See Note Q)	0.8				0.8
Stock-based compensation, net of tax	25.9		25.9
Balance, end of period at Dec. 31, 2019	$ 1,312.5	$ 2.0	$ 536.1	$ 2,734.5	$ (76.8)	$ (1,883.8)	$ 0.5
Balance, end of period, (in shares) at Dec. 31, 2019		198.8				(67.0)