Number of Properties Impaired

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- Definition

Reimbursement As Percentage Of Allowable Cost As Defined By District

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- Definition

Significant Accounting Policies [Line Items]

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- Definition

Amount of write-down of assets recognized in the income statement. Includes, but is not limited to, losses from tangible assets, intangible assets and goodwill.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 45
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=68055307&loc=d3e2420-110228

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

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- Definition

The amount of capitalized exploratory well costs that is pending the determination of proved reserves. This does not include amounts that were capitalized and subsequently expensed in the same annual period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 932
-SubTopic 235
-Section 50
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=68064819&loc=SL6806780-109447

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- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

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- Definition

A deposit made by a purchaser of real estate to evidence good faith. It is customary for a buyer to give the seller earnest money at the time a sales contract is signed. The earnest money generally is credited to the down payment at closing, which is applied at closing as a component of payment against the purchase price.

+ References

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Summary of Significant Accounting Policies - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) community_development_project	Dec. 31, 2016 USD ($) community_development_project multifamily_site	Dec. 31, 2015 USD ($)
Significant Accounting Policies [Line Items]
Non-cash impairment charges	$ 47,172,000	$ 60,939,000	$ 108,184,000
Capitalized exploratory well costs	0
Earnest money mortgages	40,408,000
Non-Oil And Gas Properties
Significant Accounting Policies [Line Items]
Depreciation expense of property and equipment	$ 441,000	889,000	$ 1,067,000
Minimum
Significant Accounting Policies [Line Items]
Reimbursement range on water, sewer and other infrastructure-related assets	70.00%
Maximum
Significant Accounting Policies [Line Items]
Reimbursement range on water, sewer and other infrastructure-related assets	90.00%
Real Estate Impairment Charges
Significant Accounting Policies [Line Items]
Non-cash impairment charges	$ 3,420,000	$ 56,453,000
Community Development Project
Significant Accounting Policies [Line Items]
Number of properties impaired \| community_development_project	1	6
Multifamily Site
Significant Accounting Policies [Line Items]
Number of properties impaired \| multifamily_site		2
Water Resources Company \| Texas
Significant Accounting Policies [Line Items]
Non-cash impairment charges	$ 3,874,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Community Development Project
Significant Accounting Policies [Line Items]
Number of properties impaired \| community_development_project		4
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Multifamily Site
Significant Accounting Policies [Line Items]
Number of properties impaired \| multifamily_site		1
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| The Mineral Companies
Significant Accounting Policies [Line Items]
Purchase price of properties sold	85,700,000
Non-cash impairment charges	37,900,000
Disposal Group, Held-for-sale, Not Discontinued Operations
Significant Accounting Policies [Line Items]
Earnest money mortgages	$ 25,712,000