Notes Payable - Terms (Details) - Home Building Consolidated - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2020	May 01, 2020	Oct. 01, 2019
Summary of unsecured homebuilding notes payable outstanding
Debt Repurchase Authorization Remaining		$ 500
Authorized Repurchase Of Debt Securities		$ 500
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
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
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
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
SeniorNoteFortyTwo [Member]
Summary of unsecured homebuilding notes payable outstanding
Date Due	Oct. 15, 2024	Oct. 15, 2024
Redeemable Prior to Maturity		Yes
Effective Interest Rate		2.70%		2.70%
Debt Instrument, Face Amount		$ 500		$ 500
SeniorNoteFortyFour
Summary of unsecured homebuilding notes payable outstanding
Date Due		Oct. 15, 2025
Redeemable Prior to Maturity		Yes
Effective Interest Rate		2.80%	2.80%
Debt Instrument, Face Amount		$ 500	$ 500