ACCOUNTS AND OTHER RECEIVABLES - Components of Accounts and Other Receivables (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020	Jan. 01, 2020
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained earnings	$ 2,924.8	$ 2,797.2
Current
Trade accounts receivable	686.0	553.5
Trade notes receivable	1.2	0.9
Total trade receivables	687.2	554.4
Other notes receivable	0.7	0.0
Taxes receivable, including income taxes	18.7	14.8
Other receivables	9.5	13.6
Subtotal other receivables	28.9	28.4
Total trade and other receivables	716.1	582.8
Allowance for doubtful accounts:
Trade accounts receivable	(17.0)	(19.2)
Trade notes receivable	0.0	0.0
Total trade receivables	(17.0)	(19.2)
Other notes receivable	0.0	0.0
Total allowance for doubtful accounts	(17.0)	(19.2)
Total receivables, net	699.1	563.6
Long-term
Trade accounts receivable	0.0	0.0
Trade notes receivable	0.3	0.3
Total trade receivables	0.3	0.3
Other notes receivable	22.7	22.8
Taxes receivable, including income taxes	0.0	0.0
Other receivables	0.0	0.0
Subtotal other receivables	22.7	22.8
Total trade and other receivables	23.0	23.1
Allowance for doubtful accounts:
Trade accounts receivable	0.0	0.0
Trade notes receivable	(0.1)	0.0
Total trade receivables	(0.1)	0.0
Other notes receivable	(22.2)	(22.8)
Total allowance for doubtful accounts	(22.3)	(22.8)
Total net receivables	0.7	0.3
Accounting Standards Update 2016-13 | Cumulative effect adjustment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Retained earnings			$ 2.5
Bedding Products
Current
Trade accounts receivable	23.2	24.6
Allowance for doubtful accounts:
Allowance for credit losses		24.6
Notes Receivable | Bedding Products
Allowance for doubtful accounts:
Allowance for credit losses	22.2	22.8
Trade Accounts Receivable | Bedding Products
Allowance for doubtful accounts:
Allowance for credit losses	$ 1.0	$ 1.8