CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2026	Mar. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Income Statement [Abstract]
Revenues	$ 374.3	$ 351.0	$ 647.3	$ 601.3
Cost of sales	294.1	271.8	512.1	467.2
Selling, general and administrative expense	37.9	38.4	74.3	74.3
Equity in earnings of unconsolidated ventures	0.0	0.0	0.0	(0.6)
Interest and other income	(1.6)	(1.0)	(3.9)	(3.3)
Loss on extinguishment of debt	0.0	1.1	0.0	1.1
Income before income taxes	43.9	40.7	64.8	62.6
Income tax expense	11.7	9.1	17.1	14.5
Net income	32.2	31.6	47.7	48.1
Net income attributable to noncontrolling interests	0.1	0.0	0.2	0.0
Net income attributable to Forestar Group Inc.	$ 32.1	$ 31.6	$ 47.5	$ 48.1
Basic net income per common share	$ 0.63	$ 0.62	$ 0.93	$ 0.95
Weighted average number of common shares	51,001,796	50,795,094	50,999,492	50,807,945
Diluted net income per common share	$ 0.63	$ 0.62	$ 0.93	$ 0.94
Adjusted weighted average number of common shares	51,209,879	51,046,724	51,195,542	51,066,321