SCHEDULE III SCHEDULE III (Details2) - USD ($)		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Balance at beginning of year	[1]	$ 2,219,448,000		$ 2,074,946,000	$ 1,927,326,000
Purchases of real estate properties		22,228,000		28,648,000	47,477,000
Development of real estate properties		203,765,000		95,032,000	97,696,000
Improvements to real estate properties		23,157,000		25,778,000	19,862,000
Carrying amount of investments sold		(61,121,000)		(4,750,000)	(17,049,000)
Write-off of improvements		(496,000)		(206,000)	(366,000)
Balance at end of year	[1]	2,406,981,000	[2],[3]	2,219,448,000	2,074,946,000
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Balance at beginning of year		657,454,000		600,526,000	550,113,000
Depreciation expense		63,793,000		59,882,000	57,303,000
Accumulated depreciation on assets sold		(26,501,000)		(2,748,000)	(6,525,000)
Other		(496,000)		(206,000)	(365,000)
Balance at end of year		694,250,000	[2],[3]	657,454,000	$ 600,526,000
Estimated aggregate cost of real estate properties for federal income tax purposes		2,370,650,000
Estimated accumulated tax depreciation		$ 467,599,000
Percentage of Occupation When Development Cost Ceased Being Capitalized		80.00%
Length of Time After Project Completion When Development Cost Ceased Being Capitalized		1 year
Secured debt		$ 257,505,000		350,285,000
Recourse liability		$ 5,000,000
Castilian Research Center [Member]
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Noncontrolling Interests (in hundreths)		20.00%
Noncontrolling Interests		$ 0		1,795,000
University Business Center [Member]
Reconciliation of Carrying Amount of Real Estate Investments [Roll Forward]
Noncontrolling Interests (in hundreths)		20.00%
Noncontrolling Interests		$ 6,853,000		6,670,000
Buildings [Member]
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Estimated useful life (in years)		40 years
Minimum [Member] | Improvements and Personal Property [Member]
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Estimated useful life (in years)		3 years
Maximum [Member] | Improvements and Personal Property [Member]
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Estimated useful life (in years)		15 years
Dominguez, Industry I and III, Kingsview, Shaw, Walnut and Washington [Member]
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Secured debt	[4]	$ 52,231,000		54,689,000
Arion 16, Broadway VI, Chino, East University I and II, Northpark, Santan 10 II, 55th Avenue and World Houston 1 and 2, 21 and 23 [Member]
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Secured debt		47,496,000		50,971,000
Colorado Crossing, Interstate I-III, Rojas, Steele Creek 1 & 2, Stemmons Circle, Venture and World Houston 3-9
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Secured debt		52,752,000		55,223,000
Arion 18, Beltway VI & VII, Commerce Park II & III, Concord Dist Ctr, Interstate Dist Ctr V, VI & VII, Lakeview Business Ctr, Ridge Creek Distribution Ctr II, Southridge IV & V and World Houston 32 [Member]
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Secured debt		44,493,000		46,584,000
Huntwood and Wiegman I Distribution Centers [Member]
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Secured debt		0		25,567,000
Alamo Downs, Arion 1-15 and 17, Rampart I-IV, Santan 10 I and World Houston 16 [Member]
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Secured debt		0		53,563,000
40th Avenue, Beltway Crossing V, Centennial Park, Executive Airport, Interchange Park I, Ocean View, Wetmore 5-8 and World Houston 26, 28, 29 and 30 [Member]
Reconciliation of Real Estate Accumulated Depreciation [Roll Forward]
Secured debt		$ 58,380,000		$ 61,312,000

[1] Includes 20% noncontrolling interests in Castilian Research Center of $0 and $1,795,000 at December 31, 2016 and 2015, respectively, and in University Business Center of $6,853,000 and $6,670,000 at December 31, 2016 and 2015, respectively.

[2] Changes in Real Estate Properties follow: Years Ended December 31,2016 2015 2014(In thousands)Balance at beginning of year $2,219,448 2,074,946 1,927,326Purchases of real estate properties 22,228 28,648 47,477Development of real estate properties203,765 95,032 97,696Improvements to real estate properties23,157 25,778 19,862Carrying amount of investments sold (61,121) (4,750) (17,049)Write-off of improvements (496) (206) (366)Balance at end of year (1) $2,406,981 2,219,448 2,074,946(1)Includes 20% noncontrolling interests in Castilian Research Center of $0 and $1,795,000 at December 31, 2016 and 2015, respectively, and in University Business Center of $6,853,000 and $6,670,000 at December 31, 2016 and 2015, respectively.Changes in the accumulated depreciation on real estate properties follow: Years Ended December 31,2016 2015 2014(In thousands)Balance at beginning of year $657,454 600,526 550,113Depreciation expense 63,793 59,882 57,303Accumulated depreciation on assets sold (26,501) (2,748) (6,525)Other (496) (206) (365)Balance at end of year $694,250 657,454 600,526

[3] The estimated aggregate cost of real estate properties at December 31, 2016 for federal income tax purposes was approximately $2,370,650,000 before estimated accumulated tax depreciation of $467,599,000. The federal income tax return for the year ended December 31, 2016, has not been filed and accordingly, this estimate is based on preliminary data.

[4] This mortgage loan has a recourse liability of $5.0 million which will be released based on the secured properties generating certain base rent amounts.