Segment Disclosures - Corporate Capital Allocation Charge (Detail) - Corporate and Reconciling Items [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Segment Reporting, Other Significant Reconciling Item [Line Items]
Corporate capital allocation charge	$ 55,438	$ 51,904	$ 160,091	$ 147,737
Home Building [Member] | Mid Atlantic [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Corporate capital allocation charge	31,733	32,025	93,682	92,154
Home Building [Member] | North East [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Corporate capital allocation charge	4,565	4,244	13,325	12,191
Home Building [Member] | Mid East [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Corporate capital allocation charge	9,541	7,747	26,571	22,024
Home Building [Member] | South East [Member]
Segment Reporting, Other Significant Reconciling Item [Line Items]
Corporate capital allocation charge	$ 9,599	$ 7,888	$ 26,513	$ 21,368