Quarterly Results (unaudited) - Quarterly Financial Data and Operating Information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015 USD ($) Contract Settlements Backlog $ / shares	Sep. 30, 2015 USD ($) Contract Settlements Backlog $ / shares	Jun. 30, 2015 USD ($) Contract Settlements Backlog $ / shares	Mar. 31, 2015 USD ($) Contract Settlements Backlog $ / shares	Dec. 31, 2014 USD ($) Contract Settlements Backlog $ / shares	Sep. 30, 2014 USD ($) Contract Settlements Backlog $ / shares	Jun. 30, 2014 USD ($) Contract Settlements Backlog $ / shares	Mar. 31, 2014 USD ($) Contract Settlements Backlog $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 USD ($) $ / shares
Quarterly Financial Information [Line Items]
Net income	$ 134,004	$ 116,470	$ 93,395	$ 39,058	$ 99,451	$ 90,152	$ 68,178	$ 23,849	$ 382,927	$ 281,630	$ 266,477
Diluted earnings per share | $ / shares	$ 31.92	$ 27.11	$ 21.91	$ 9.22	$ 23.24	$ 20.70	$ 15.17	$ 5.16	$ 89.99	$ 63.50	$ 54.81
Contracts for sale, net of cancellations (units) | Contract	3,100	3,258	3,796	3,926	2,713	2,936	3,415	3,325
Settlements (units) | Settlements	4,010	3,607	3,175	2,534	3,469	3,236	2,943	2,211
Backlog, end of period (units) | Backlog	6,229	7,139	7,488	6,867	5,475	6,231	6,531	6,059
Loans closed	$ 1,042,440	$ 951,872	$ 859,403	$ 638,627	$ 881,930	$ 803,125	$ 675,625	$ 472,933
Homebuilding [Member]
Quarterly Financial Information [Line Items]
Revenues – homebuilding operations	1,528,084	1,374,467	1,221,111	941,538	1,306,632	1,185,160	1,084,080	799,187	$ 5,065,200	$ 4,375,059	$ 4,134,481
Gross profit – homebuilding operations	289,496	262,795	234,257	159,870	236,031	225,105	201,302	144,035
Mortgage Banking [Member]
Quarterly Financial Information [Line Items]
Mortgage banking fees	$ 27,191	$ 27,884	$ 22,522	$ 16,211	$ 21,406	$ 18,006	$ 17,974	$ 12,123	$ 93,808	$ 69,509	$ 76,786