Real Estate - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017 USD ($) a community_development_project	Dec. 31, 2016 USD ($) a property room community_development_project multifamily_site	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Real Estate Properties [Line Items]
Cost of asset in developed and under development projects	$ 27,915,000
Recovery of direct costs	(20,071,000)	$ (27,107,000)	$ (15,176,000)
Non-cash impairment charges	47,172,000	60,939,000	108,184,000
Gain of sale of assets	113,411,000	166,747,000	1,585,000
Payment of debt	10,049,000	315,229,000	58,220,000
Utility and Improvement District
Real Estate Properties [Line Items]
Cost of asset in developed and under development projects	9,775,000	45,157,000
Cibolo Canyons Project | San Antonio, Texas
Real Estate Properties [Line Items]
Cost of asset in developed and under development projects	14,127,000	14,749,000
Consolidated Properties
Real Estate Properties [Line Items]
Recovery of direct costs	19,606,000
Income Producing Properties | Land, Buildings and Improvements
Real Estate Properties [Line Items]
Depreciation expense, related to commercial and income producing properties	0	816,000	$ 6,810,000
Radisson Hotel & Suites, Austin | Austin, Texas
Real Estate Properties [Line Items]
Sales price		130,000,000
Net proceeds		128,764,000
Gain of sale of assets		$ 95,336,000
Number of hotel rooms | room		413
Payment of debt		$ 15,400,000
Eleven | Multi Family Property | Austin, Texas
Real Estate Properties [Line Items]
Sales price		60,150,000
Net proceeds		59,719,000
Gain of sale of assets		9,116,000
Payment of debt		$ 23,936,000
Number of units of multifamily project | property		257
Dillon | Charlotte, North Carolina
Real Estate Properties [Line Items]
Sales price		$ 25,979,000
Net proceeds		25,428,000
Gain of sale of assets		$ 1,223,000
Number of units of multifamily project | property		379
Music Row | Nashville, Tennessee
Real Estate Properties [Line Items]
Sales price		$ 15,025,000
Net proceeds		14,703,000
Gain of sale of assets		$ 3,968,000
Number of units of multifamily project | property		230
Downtown Edge | Austin, Texas
Real Estate Properties [Line Items]
Sales price		$ 5,000,000
Net proceeds		4,975,000
Gain of sale of assets		(3,870,000)
Real Estate Impairment Charges
Real Estate Properties [Line Items]
Non-cash impairment charges	$ 3,420,000	$ 56,453,000
Community Development Project
Real Estate Properties [Line Items]
Number of properties impaired | community_development_project	1	6
Multifamily Site
Real Estate Properties [Line Items]
Number of properties impaired | multifamily_site		2
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Georgia and Texas
Real Estate Properties [Line Items]
Area of land (in acres) | a	19,000
Sales price	$ 46,197,000
Net proceeds	45,396,000
Gain of sale of assets	28,674,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Georgia and Alabama
Real Estate Properties [Line Items]
Area of land (in acres) | a		58,300
Sales price		$ 104,172,000
Net proceeds		103,238,000
Gain of sale of assets		$ 48,891,000
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Community Development Project
Real Estate Properties [Line Items]
Number of properties impaired | community_development_project		4
Disposal Group, Disposed of by Sale, Not Discontinued Operations | Multifamily Site
Real Estate Properties [Line Items]
Number of properties impaired | multifamily_site		1
Bonds | Cibolo Canyons Project | San Antonio, Texas
Real Estate Properties [Line Items]
Payments received from special improvement district				$ 50,550,000
Debt instrument, face amount				48,900,000
Letters of credit outstanding, amount				$ 6,846,000
Surety bond for bond trustee	$ 5,312,000