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		6 Months Ended
	Jun. 28, 2025	Jun. 29, 2024	Jun. 28, 2025	Jun. 29, 2024
Numerator:
Numerator for both basic and diluted EPS attributable to HNI Corporation net income	$ 48.2	$ 36.0	$ 62.2	$ 53.7
Denominators:
Denominator for basic EPS weighted-average common shares outstanding (in shares)	46.2	47.2	46.6	47.1
Potentially dilutive shares from stock-based compensation plans (in shares)	1.0	1.0	1.0	1.1
Denominator for diluted EPS (in shares)	47.1	48.2	47.6	48.2
Earnings per share - basic (in dollars per share)	$ 1.04	$ 0.76	$ 1.33	$ 1.14
Earnings per share - diluted (in dollars per share)	$ 1.02	$ 0.75	$ 1.31	$ 1.11