Segment Information, Nature of Operations, and Certain Concentrations - Depreciation and Amortization (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	$ 22,667	$ 22,269	$ 21,534
Profit before taxes:
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	17,547	17,283	16,777
Profit before taxes: | Homebuilding: | Mid Atlantic
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	8,095	8,089	7,876
Profit before taxes: | Homebuilding: | North East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	2,034	2,053	1,571
Profit before taxes: | Homebuilding: | Mid East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	3,590	3,748	4,003
Profit before taxes: | Homebuilding: | South East
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	2,531	2,276	2,191
Profit before taxes: | Mortgage Banking:
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	1,297	1,117	1,136
Other unallocated interest income
Segment Reporting, Other Significant Reconciling Item [Line Items]
Consolidated depreciation and amortization	$ 5,120	$ 4,986	$ 4,757