Earnings Per Share - Schedule of Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 27, 2025	Sep. 28, 2024	Sep. 27, 2025	Sep. 28, 2024
Numerator:
Numerator for both basic and diluted EPS attributable to HNI Corporation net income	$ 41.2	$ 47.5	$ 103.4	$ 101.2
Denominators:
Denominator for basic EPS weighted-average common shares outstanding (in shares)	45.8	47.7	46.3	47.3
Potentially dilutive shares from stock-based compensation plans (in shares)	0.9	1.1	1.0	1.0
Denominator for diluted EPS (in shares)	46.7	48.7	47.3	48.4
Earnings per share - basic (in dollars per share)	$ 0.90	$ 1.00	$ 2.23	$ 2.14
Earnings per share - diluted (in dollars per share)	$ 0.88	$ 0.98	$ 2.19	$ 2.09