Commitments and Contingencies Commitments and Contingencies (Details) $ in Thousands	Dec. 31, 2017 USD ($)
Commitments and Contingencies [Abstract]
Letters of Credit and Completion Bonds	$ 179,563
Outstanding Performance and Maintenance Bonds	122,294
Performance letters of credit outstanding	41,550
Financial Letters of Credit	8,103
Financial Letters of Credit representing deposits on land and lot purchase agreements	7,249
Financial Bonds	7,616
Unrecorded Conditional Purchase Obligation	$ 715,716