Net Income (Loss) per Share - Earnings Attributable to Common Shareholders and Weighted Average Common Shares Outstanding - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Continuing operations
Net income (loss) attributable to Forestar Group Inc.	$ 9.6	$ 10.1	$ 26.4	$ 13.4
Denominator:
Weighted average common shares outstanding — basic	48,025,359	41,959,866	48,018,246	41,956,179
Dilutive effect of share based compensation	57,592	6,233	56,439	6,220
Total weighted average shares outstanding — diluted	48,082,951	41,966,099	48,074,685	41,962,399
Earnings Per Share, Basic	$ 0.20	$ 0.24	$ 0.55	$ 0.32
Earnings Per Share, Diluted	$ 0.20	$ 0.24	$ 0.55	$ 0.32