Commitments and Contingencies Commitments and Contingencies (Details) $ in Millions	Sep. 30, 2020 USD ($)
Commitments and Contingencies [Abstract]
Letters of credit and completion bonds	$ 267.7
Performance bonds outstanding	194.1
Performance letters of credit outstanding	55.1
Financial letters of credit	11.5
Financial letters of credit representing deposits on land and lot purchase agreements	11.0
Financial Bonds	7.0
Unrecorded conditional purchase obligation	$ 801.4