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
	Mar. 29, 2025	Mar. 30, 2024
Numerator:
Numerator for both basic and diluted EPS attributable to HNI Corporation net income	$ 13.9	$ 17.7
Denominators:
Denominator for basic EPS weighted-average common shares outstanding (in shares)	47.0	47.1
Potentially dilutive shares from stock-based compensation plans (in shares)	1.0	1.0
Denominator for diluted EPS (in shares)	48.0	48.1
Earnings per share - basic (in dollars per share)	$ 0.30	$ 0.38
Earnings per share - diluted (in dollars per share)	$ 0.29	$ 0.37