CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Millions	3 Months Ended
	Dec. 31, 2022	Dec. 31, 2021
Earnings Per Share, Diluted [Abstract]
Revenues	$ 216.7	$ 407.6
Cost of sales	169.2	334.2
Selling, general and administrative expense	22.9	21.5
Equity in earnings of unconsolidated ventures	0.0	(1.1)
Gain on sale of assets	(1.6)	(0.5)
Interest and other income	(1.7)	0.0
Income before income taxes	27.9	53.5
Income tax expense	7.1	13.0
Net income	20.8	40.5
Net income attributable to noncontrolling interests	0.0	0.0
Net income attributable to Forestar Group Inc.	$ 20.8	$ 40.5
Basic net income per common share attributable to Forestar Group Inc.	$ 0.42	$ 0.81
Weighted average number of common shares	49,890,481	49,683,369
Diluted net income per common share attributable to Forestar Group Inc.	$ 0.42	$ 0.81
Adjusted weighted average number of common shares	49,899,022	49,732,869