Commitments and Contingencies Commitments and Contingencies (Details) $ in Millions	Sep. 30, 2021 USD ($)
Commitments and Contingencies [Abstract]
Letters of credit and completion bonds	$ 363.6
Performance bonds outstanding	263.6
Performance letters of credit outstanding	81.4
Financial letters of credit	13.0
Financial letters of credit representing deposits on land and lot purchase agreements	12.6
Financial Bonds	5.6
Unrecorded conditional purchase obligation	$ 866.7