Real Estate Inventories - Additional Information (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) Project	Dec. 31, 2016 USD ($) Project
Real Estate Properties [Line Items]
Number of projects classified as held for sale \| Project	0	0
Impairment (reversal) charges	$ 526	$ 2,425
Washington D.C. [Member]
Real Estate Properties [Line Items]
Impairment (reversal) charges	$ 500	2,400
Settlement Agreement [Member] \| Washington D.C. [Member]
Real Estate Properties [Line Items]
Portion of land purchase deposit refundable		$ 700

The charge against earnings in the period to reduce the carrying amount of real property to fair value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84176398&loc=d3e2921-110230

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Name:	us-gaap_ImpairmentOfRealEstate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration