Segment Disclosures - Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	$ 3,843,359		$ 3,165,933
Operating lease right-of-use assets		$ 79,345
Contract land deposit reserve	(27,644)		(29,216)
Home Building [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	3,353,866		2,641,511
Cash and cash equivalents	1,068,172		688,783
Operating lease right-of-use assets	63,505		0
Mortgage Banking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	489,493		524,422
Cash and cash equivalents	26,765		23,092
Operating lease right-of-use assets	13,857		0
Operating Segments [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	2,514,747		2,303,723
Operating Segments [Member] | Home Building [Member] | Mid Atlantic [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,122,806		1,018,953
Operating Segments [Member] | Home Building [Member] | North East [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	176,567		144,412
Operating Segments [Member] | Home Building [Member] | Mid East [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	322,672		290,815
Operating Segments [Member] | Home Building [Member] | South East [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	410,556		332,468
Operating Segments [Member] | Mortgage Banking [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	482,146		517,075
Corporate and Reconciling Items [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Total assets	1,328,612		862,210
Cash and cash equivalents	1,068,172		688,783
Deferred taxes	114,579		112,333
Intangible assets and goodwill	49,872		49,989
Operating lease right-of-use assets	63,505		0
Contract land deposit reserve	(27,644)		(29,216)
Consolidation adjustments and other	$ 60,128		$ 40,321