Acquisitions and Divestitures - Narrative (Details) $ / shares in Units, $ in Millions			1 Months Ended	3 Months Ended	9 Months Ended
	Aug. 08, 2025 shares	Aug. 03, 2025 USD ($) day board_member $ / shares	Apr. 30, 2025 USD ($)	Sep. 27, 2025 USD ($)	Sep. 27, 2025 USD ($)
Other Assets
Business Combination [Line Items]
Addition capitalized costs				$ 3.3	$ 3.3
Prepaid Expenses and Other Current Assets
Business Combination [Line Items]
Addition capitalized costs				1.4	1.4
Equity Attributable to Parent
Business Combination [Line Items]
Addition capitalized costs				1.0	1.0
Selling, General and Administrative Expenses
Business Combination [Line Items]
Acquisition related expenses				8.3
Nonoperating Income (Expense)
Business Combination [Line Items]
Acquisition related expenses				1.4
Discontinued Operations, Disposed of by Sale | HNI India
Business Combination [Line Items]
Gross cash proceeds related to sale			$ 9.5
Net of cash and transaction fees			8.1
Pre-tax loss on the sale					$ 6.6
Foreign currency translation loss			6.0
Transaction-related expenses			$ 0.6
Common Class A | Steelcase Inc
Business Combination [Line Items]
Common stock, par value (in dollars per share) | $ / shares		$ 0
Common stock, shares outstanding (in shares) | shares	114,717,466
Common Class B | Steelcase Inc
Business Combination [Line Items]
Common stock, par value (in dollars per share) | $ / shares		0
Common stock, shares outstanding (in shares) | shares	0
Steelcase Inc
Business Combination [Line Items]
Total consideration				$ 2,100.0
Common stock, par value (in dollars per share) | $ / shares		$ 1.00
Share conversion ratio		0.2192
Mixed consideration (in dollars per share) | $ / shares		$ 7.20
Threshold consecutive trading days | day		10
Increase in board members | board_member		2
Number of board members | board_member		12
Number of board members from aquiree | board_member		2
Steelcase Inc | Line of Credit
Business Combination [Line Items]
Borrowings		$ 925.0
Steelcase Inc | Minimum
Business Combination [Line Items]
Termination fee payable		71.0
Steelcase Inc | Maximum
Business Combination [Line Items]
Termination fee payable		134.0
Steelcase Inc | Steelcase Inc
Business Combination [Line Items]
Termination fee payable		$ 67.0
Steelcase Inc | Common Class A | Steelcase Inc
Business Combination [Line Items]
Total number of shares for cash consideration (in shares) | shares	2,216,114
Steelcase Inc | Common Class B | Steelcase Inc
Business Combination [Line Items]
Total number of shares for cash consideration (in shares) | shares	2,216,114