Restructuring, Impairment, and Loss on Divestiture - Schedule of Restructuring and Related Costs (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jul. 04, 2026	Jun. 28, 2025	Jul. 04, 2026	Jun. 28, 2025
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 23.8	$ 2.6	$ 44.3	$ 10.5
Facility closure and consolidation costs \| Workplace furnishings
Restructuring Cost and Reserve [Line Items]
Restructuring costs	5.5	0.1	8.0	1.6
Facility closure and consolidation costs \| Residential building products
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.5	0.0	0.5	0.0
Divestiture of HNI India \| Workplace furnishings
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.0	(0.1)	0.0	5.8
Divestiture of HNI India \| General Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.0	0.6	0.0	0.6
Structural cost actions \| Workplace furnishings
Restructuring Cost and Reserve [Line Items]
Restructuring costs	11.1	2.1	19.5	2.6
Structural cost actions \| General Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.3	0.0	0.3	0.0
Long-lived asset impairments \| Workplace furnishings
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0.0	0.0	9.5	0.0
Long-lived asset impairments \| Residential building products
Restructuring Cost and Reserve [Line Items]
Restructuring costs	5.6	0.0	5.6	0.0
Structural cost actions \| Residential building products
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 0.9	$ 0.0	$ 0.9	$ 0.0