Segment Information, Nature of Operations, and Certain Concentrations - Depreciation and Amortization (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	$ 21,992	$ 20,818	$ 20,168
Profit before taxes:
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	18,745	17,495	16,846
Profit before taxes: | Home Building | Mid Atlantic
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	6,806	7,069	7,753
Profit before taxes: | Home Building | North East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	1,800	1,411	1,600
Profit before taxes: | Home Building | Mid East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	4,969	4,348	3,481
Profit before taxes: | Home Building | South East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	3,636	3,086	2,523
Profit before taxes: | Mortgage Banking
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	1,534	1,581	1,489
Other unallocated interest income
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	$ 3,247	$ 3,323	$ 3,322