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. 29, 2024	Jul. 01, 2023	Jun. 29, 2024	Jul. 01, 2023
Numerator:
Numerator for both basic and diluted EPS attributable to HNI Corporation net income (loss)	$ 36.0	$ (12.8)	$ 53.7	$ (11.3)
Denominators:
Denominator for basic EPS weighted-average common shares outstanding (in shares)	47.2	43.3	47.1	42.4
Potentially dilutive shares from stock-based compensation plans (in shares)	1.0	0.0	1.1	0.0
Denominator for diluted EPS (in shares)	48.2	43.3	48.2	42.4
Earnings per share - basic (in dollars per share)	$ 0.76	$ (0.30)	$ 1.14	$ (0.27)
Earnings per share - diluted (in dollars per share)	$ 0.75	$ (0.30)	$ 1.11	$ (0.27)