Commitments and Contingencies (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Mar. 31, 2015
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Dec. 31, 2014
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Dec. 31, 2013
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Commitments and Contingencies            
Mortgage loan types originated (as a percent) 100.00% 100.00% 100.00% 100.00% 100.00% 100.00%
Average FICO credit score 729 732 733 731 726 723
Average combined loan-to-value ratio (as a percent) 87.80% 87.80% 89.80% 90.10% 90.30% 90.80%
Mortgage interest rate lock commitments ("IRLCs")            
Commitments and Contingencies            
Average number of days of interest rate commitment before closing 180 days          
Interest rate, low end range 3.40% 3.40%        
Interest rate, high end range 4.80% 4.80%        
Notional amount 231.9 148.0        
Development bonds            
Commitments and Contingencies            
Guarantee obligations estimated exposure pertaining to land development and improvements 194.5 189.4        
Performance-related cash deposits and letters of credit            
Commitments and Contingencies            
Guarantee obligations estimated exposure pertaining to land development and improvements 84.2 87.3        
Prime            
Commitments and Contingencies            
Mortgage loan types originated (as a percent) 68.10% 67.60% 57.20% 48.60% 42.20% 34.90%
Government (FHA/VA/USDA)
           
Commitments and Contingencies            
Mortgage loan types originated (as a percent) 31.90% 32.40% 42.80% 51.40% 57.80% 65.10%
Lot option purchase contracts            
Commitments and Contingencies            
Cash deposits and/or letters of credit 74.3 72.8        
Aggregate purchase price 781.7 847.1        
Purchase commitments, specific performance 1.4 1.4