Quarterly Results (unaudited) - Quarterly Financial Data and Operating Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014 Contract Settlements Backlog	Sep. 30, 2014 Settlements Contract Backlog	Jun. 30, 2014 Backlog Contract Settlements	Mar. 31, 2014 Contract Backlog Settlements	Dec. 31, 2013 Contract Settlements Backlog	Sep. 30, 2013 Backlog Contract Settlements	Jun. 30, 2013 Settlements Backlog Contract	Mar. 31, 2013 Settlements Backlog Contract	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information [Line Items]
Net income	$ 99,451	$ 90,152	$ 68,178	$ 23,849	$ 97,811	$ 82,935	$ 50,690	$ 35,041	$ 281,630	$ 266,477	$ 180,588
Diluted earnings per share	$ 23.24	$ 20.70	$ 15.17	$ 5.16	$ 21.15	$ 17.67	$ 10.11	$ 6.84	$ 63.50	$ 54.81	$ 35.12
Contracts for sale, net of cancellations (units)	2,713	2,936	3,415	3,325	2,631	2,381	3,278	3,510
Settlements (units)	3,469	3,236	2,943	2,211	3,342	3,342	2,878	2,272
Backlog, end of period (units)	5,475	6,231	6,531	6,059	4,945	5,656	6,617	6,217
Loans closed	881,930	803,125	675,625	472,933	721,926	695,930	646,450	473,766
Homebuilding [Member]
Quarterly Financial Information [Line Items]
Revenues – homebuilding operations	1,306,632	1,185,160	1,084,080	799,187	1,223,808	1,167,595	992,210	750,868	4,375,059	4,134,481	3,121,244
Gross profit – homebuilding operations	236,031	225,105	201,302	144,035	222,393	203,179	157,922	126,783
Mortgage Banking [Member]
Quarterly Financial Information [Line Items]
Mortgage banking fees	$ 21,406	$ 18,006	$ 17,974	$ 12,123	$ 18,344	$ 21,372	$ 17,682	$ 19,388	$ 69,509	$ 76,786	$ 63,406