Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Earnings Per Share Reconciliation [Abstract]
Net Income (Loss) Attributable to Parent	$ 4,175.8	$ 2,373.7	$ 1,618.5
Denominator:
Denominator for basic earnings per share - weighted average common shares	361.1	365.5	372.6
Effect of dilutive securities:
Employee stock awards	4.7	4.7	4.8
Denominator for diluted earnings per share - adjusted weighted average common shares	365.8	370.2	377.4
Basic net income per common share attributable to D.R. Horton, Inc.	$ 11.56	$ 6.49	$ 4.34
Diluted net income per common share attributable to D.R. Horton, Inc.	$ 11.41	$ 6.41	$ 4.29