Segment Disclosures - Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 5,499,920	$ 3,809,815
Contract land deposit reserve	(58,781)	(27,572)
Home Building [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	5,088,695	3,242,061
Cash and cash equivalents	2,539,460	1,110,892
Operating lease right-of-use assets	54,964	63,825
Mortgage Banking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	411,225	567,754
Cash and cash equivalents	21,546	29,412
Operating lease right-of-use assets	13,376	13,345
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	2,671,242	2,447,015
Operating Segments [Member] | Home Building [Member] | Mid Atlantic [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,198,050	1,024,996
Operating Segments [Member] | Home Building [Member] | North East [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	199,162	166,860
Operating Segments [Member] | Home Building [Member] | Mid East [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	395,668	293,773
Operating Segments [Member] | Home Building [Member] | South East [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	474,484	400,979
Operating Segments [Member] | Mortgage Banking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	403,878	560,407
Corporate and Reconciling Items [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	2,828,678	1,362,800
Cash and cash equivalents	2,539,460	1,110,892
Deferred taxes	125,743	115,731
Intangible assets and goodwill	49,717	49,834
Operating lease right-of-use assets	54,964	63,825
Finance Lease, Right-of-Use Asset, after Accumulated Amortization	15,674	7,052
Contract land deposit reserve	(58,781)	(27,572)
Consolidation adjustments and other	$ 101,901	$ 43,038