Quarterly Results (unaudited) - Quarterly Financial Data and Operating Information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016 USD ($) Order Settlements Backlog $ / shares	Sep. 30, 2016 USD ($) Order Settlements Backlog $ / shares	Jun. 30, 2016 USD ($) Order Settlements Backlog $ / shares	Mar. 31, 2016 USD ($) Order Settlements Backlog $ / shares	Dec. 31, 2015 USD ($) Order Settlements Backlog $ / shares	Sep. 30, 2015 USD ($) Order Settlements Backlog $ / shares	Jun. 30, 2015 USD ($) Order Settlements Backlog $ / shares	Mar. 31, 2015 USD ($) Order Settlements Backlog $ / shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares
Quarterly Financial Information [Line Items]
Net income	$ 150,891	$ 117,392	$ 91,676	$ 65,303	$ 134,004	$ 116,470	$ 93,395	$ 39,058	$ 425,262	$ 382,927	$ 281,630
Diluted earnings per share | $ / shares	$ 37.80	$ 28.46	$ 22.01	$ 15.79	$ 31.92	$ 27.11	$ 21.91	$ 9.22	$ 103.61	$ 89.99	$ 63.50
New orders (units) | Order	3,645	3,477	4,324	4,137	3,100	3,258	3,796	3,926
Settlements (units) | Settlements	4,419	3,922	3,581	3,006	4,010	3,607	3,175	2,534
Backlog, end of period (units) | Backlog	6,884	7,658	8,103	7,360	6,229	7,139	7,488	6,867
Loans closed	$ 1,201,164	$ 1,055,163	$ 942,407	$ 753,840	$ 1,042,440	$ 951,872	$ 859,403	$ 638,627
Homebuilding [Member]
Quarterly Financial Information [Line Items]
Revenues – homebuilding operations	1,718,527	1,507,451	1,361,741	1,121,504	1,528,084	1,374,467	1,221,111	941,538	$ 5,709,223	$ 5,065,200	$ 4,375,059
Gross profit – homebuilding operations	305,087	265,159	235,372	195,744	289,496	262,795	234,257	159,870
Mortgage Banking [Member]
Quarterly Financial Information [Line Items]
Mortgage banking fees	$ 34,239	$ 30,118	$ 26,442	$ 22,522	$ 27,191	$ 27,884	$ 22,522	$ 16,211	$ 113,321	$ 93,808	$ 69,509