Segment Information, Nature of Operations, and Certain Concentrations - Expenditures for Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	$ 22,699	$ 19,665	$ 20,269
Profit before taxes:
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	21,282	16,442	19,709
Profit before taxes: | Homebuilding: | Mid Atlantic
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	9,218	6,657	9,257
Profit before taxes: | Homebuilding: | North East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	2,000	1,074	1,299
Profit before taxes: | Homebuilding: | Mid East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	5,221	4,302	3,117
Profit before taxes: | Homebuilding: | South East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	3,944	2,732	3,313
Profit before taxes: | Mortgage Banking:
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	899	1,677	2,723
Other unallocated interest income
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	$ 1,417	$ 3,223	$ 560