Results of Quarterly Operations (Unaudited) - Results of Quarterly Operations (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues	$ 1,225,166	$ 1,037,352	$ 919,722	$ 718,971	$ 1,104,468	$ 772,662	$ 751,441	$ 664,682	$ 3,901,211	$ 3,293,253	$ 3,065,216
Asset impairments	$ 0	$ 0	$ 0	$ 0	$ (325)	$ 0	$ 0	$ (610)
Gross margin from home sales (including impairments)	22.00%	20.50%	20.20%	19.90%	18.50%	18.80%	19.50%	18.90%
Homebuilding selling, general and administrative expenses	$ 117,949	$ 103,632	$ 92,316	$ 89,321	$ 105,101	$ 92,716	$ 82,712	$ 82,261
Income before income taxes	171,294	126,018	111,638	48,562	112,246	62,806	74,331	55,606	457,512	304,989	263,854
Net Income	$ 147,488	$ 98,938	$ 84,396	$ 36,760	$ 92,589	$ 50,580	$ 54,593	$ 40,550	$ 367,582	$ 238,312	$ 210,780
Basic ( in dollars per share)	$ 2.27	$ 1.54	$ 1.33	$ 0.58	$ 1.48	$ 0.81	$ 0.88	$ 0.66	$ 5.76	$ 3.84	$ 3.46
Diluted (in dollars per share)	$ 2.19	$ 1.49	$ 1.31	$ 0.56	$ 1.42	$ 0.79	$ 0.86	$ 0.64	$ 5.58	$ 3.72	$ 3.39
Home Building
Disaggregation of Revenue [Line Items]
Revenues	$ 1,180,987	$ 1,000,549	$ 886,758	$ 697,085	$ 1,074,852	$ 750,274	$ 732,844	$ 647,278