Investment in Unconsolidated and Consolidated Joint Ventures - Investment Information (Details)	1 Months Ended	3 Months Ended			6 Months Ended
	Sep. 30, 2016 ft²	Jun. 30, 2018 USD ($) a	Jun. 30, 2017 USD ($)	Jun. 30, 2013 USD ($) ft² member	Jun. 30, 2018 USD ($) a ft² joint_venture	Jun. 30, 2017 USD ($)	Jun. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2013 USD ($)
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures		$ 30,742,000			$ 30,742,000			$ 30,031,000
Equity in earnings (loss)		652,000	$ 1,560,000		819,000	$ 1,788,000
Equity		30,742,000			30,742,000			30,031,000
Debt		$ 119,540,000			$ 119,540,000			114,273,000
Promissory note agreement
Schedule of Equity Method Investments [Line Items]
Debt instrument face amount									$ 4,750,000
Petro Travel Plaza Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Unconsolidated joint ventures, ownership interest		50.00%			50.00%
Right and share of profit and loss		60.00%			60.00%
Equity		$ 19,128,000			$ 19,128,000			17,422,000
Debt		15,281,000			15,281,000			15,280,000
Majestic Realty Co.
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures		$ 24,773,000			$ 24,773,000
Unconsolidated joint ventures, ownership interest		50.00%			50.00%
Number of joint venture contracts | joint_venture					2
Investment in unconsolidated joint ventures		$ 770,000			$ 770,000
Area of building owned and leased | ft²					651,909
TRC-MRC 2, LLC
Schedule of Equity Method Investments [Line Items]
Equity		0			$ 0			0
Debt instrument face amount							$ 25,240,000
Debt		(25,240,000)			(25,240,000)			21,080,000
Deficit balance		716,000			716,000
TRCC-East
Schedule of Equity Method Investments [Line Items]
Area of building owned and leased | ft²	480,480
Deficit balance		54,000			54,000
Number of acres for development | ft²				326,000
TRC-MRC 1, LLC
Schedule of Equity Method Investments [Line Items]
Equity		0			0			0
Debt		21,779,000			21,779,000			19,433,000
Construction Loan		25,000,000			$ 25,000,000
Rockefeller Joint Ventures
Schedule of Equity Method Investments [Line Items]
Number of joint venture contracts | joint_venture					3
Investment in unconsolidated joint ventures		$ 11,614,000			$ 11,614,000
Number of acres for development | a					91
Development of land in TRCC including pursuing foreign trade zone (up to) | a		500			500
Rockefeller Joint Ventures | Building Development
Schedule of Equity Method Investments [Line Items]
Number of joint venture contracts | joint_venture					2
Five West Parcel, LLC
Schedule of Equity Method Investments [Line Items]
Unconsolidated joint ventures, ownership interest		50.00%			50.00%
Equity		$ 3,010,000			$ 3,010,000			2,802,000
Area of building owned and leased | ft²					606,000
Debt		9,442,000			$ 9,442,000			9,711,000
18-19 West, LLC
Schedule of Equity Method Investments [Line Items]
Equity		1,756,000			1,756,000			1,782,000
Debt		0			$ 0			0
Number of acres for development | a					61.5
TRCC/Rock Outlet Center, LLC
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures				$ 87,000,000
Equity		6,848,000			$ 6,848,000			8,025,000
Debt		47,798,000			47,798,000			48,769,000
Construction loan percent of costs				60.00%
Equity contributions, percent				40.00%
Number of members | member				2
TRCC/Rock Outlet Center, LLC | Line of Credit
Schedule of Equity Method Investments [Line Items]
Summarized financial information, maximum borrowing capacity		52,000,000			52,000,000
Centennial
Schedule of Equity Method Investments [Line Items]
Debt		0			0			$ 0
Noncontrolling interest balance		$ 11,039,000			$ 11,039,000
Consolidated joint venture, ownership interest		90.89%			90.89%