Segment Information, Nature of Operations, and Certain Concentrations - Expenditures for Property and Equipment (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	$ 16,119	$ 22,699	$ 19,665
Profit before taxes:
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	15,919	21,282	16,442
Profit before taxes: | Home Building | Mid Atlantic
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	5,712	9,218	6,657
Profit before taxes: | Home Building | North East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	1,083	2,000	1,074
Profit before taxes: | Home Building | Mid East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	5,041	5,221	4,302
Profit before taxes: | Home Building | South East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	3,818	3,944	2,732
Profit before taxes: | Mortgage Banking
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	265	899	1,677
Other unallocated interest income
Segment Reporting, Other Significant Reconciling Item [Line Items]
Expenditures for property and equipment:	$ 200	$ 1,417	$ 3,223