Commitments and Contingencies (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2012 Score	Dec. 31, 2011 Score	Dec. 31, 2010 Score	Dec. 31, 2009 Score	Dec. 31, 2008 Score	Dec. 31, 2007 Score
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	726	723	717	711	713
Average combined loan-to-value ratio (as a percent)	90.50%	90.30%	90.80%	91.40%	90.10%	89.10%
Mortgage interest rate lock commitments ("IRLCs")
Commitments and Contingencies
Average number of days of interest rate commitment before closing	180 days
Notional amount	156,800,000	114,600,000
Development bonds
Commitments and Contingencies
Guarantee obligations estimated exposure pertaining to land development and improvements	98,000,000	93,900,000
Performance-related cash deposits and letters of credit
Commitments and Contingencies
Guarantee obligations estimated exposure pertaining to land development and improvements	49,100,000	37,200,000
Prime
Commitments and Contingencies
Mortgage loan types originated (as a percent)	45.20%	42.20%	34.90%	32.90%	51.80%	72.00%
Government (FHA/VA)
Commitments and Contingencies
Mortgage loan types originated (as a percent)	54.80%	57.80%	65.10%	67.10%	48.20%	20.10%
Alt A
Commitments and Contingencies
Mortgage loan types originated (as a percent)	0.00%	0.00%	0.00%	0.00%	0.00%	7.50%
Subprime
Commitments and Contingencies
Mortgage loan types originated (as a percent)	0.00%	0.00%	0.00%	0.00%	0.00%	0.40%
Lot option purchase contracts
Commitments and Contingencies
Cash deposits and/or letters of credit	54,400,000	51,900,000
Aggregate purchase price	532,300,000	407,600,000
Purchase commitments, specific performance	765,000	1,000,000