Notes Payable - Terms (Details) - Home Building [Member] $ in Millions	12 Months Ended
	Sep. 30, 2019 USD ($)
Senior Note Member Thirty [Member]
Summary of unsecured homebuilding notes payable outstanding
Date Due	Feb. 15, 2020
Redeemable Prior to Maturity	Yes
Effective Interest Rate	4.20%
Debt Instrument, Face Amount	$ 500.0
Senior Note Member Thirty-One [Member]
Summary of unsecured homebuilding notes payable outstanding
Date Due	Dec. 01, 2020
Redeemable Prior to Maturity	Yes
Effective Interest Rate	2.80%
Debt Instrument, Face Amount	$ 400.0
Senior Note Member Twenty Five [Member]
Summary of unsecured homebuilding notes payable outstanding
Date Due	Sep. 15, 2022
Redeemable Prior to Maturity	Yes
Effective Interest Rate	4.50%
Debt Instrument, Face Amount	$ 350.0
Senior Note Twenty Seven [Member]
Summary of unsecured homebuilding notes payable outstanding
Date Due	Feb. 15, 2023
Redeemable Prior to Maturity	Yes
Effective Interest Rate	4.90%
Debt Instrument, Face Amount	$ 300.0
SeniorNoteTwentyEight [Member]
Summary of unsecured homebuilding notes payable outstanding
Date Due	Aug. 15, 2023
Redeemable Prior to Maturity	Yes
Effective Interest Rate	5.90%
Debt Instrument, Face Amount	$ 400.0