Investment in Unconsolidated and Consolidated Joint Ventures - Investment Information (Details)	1 Months Ended	3 Months Ended			19 Months Ended
	Sep. 30, 2016 ft²	Mar. 31, 2018 USD ($) a ft² joint_venture	Mar. 31, 2017 USD ($)	Jun. 30, 2013 USD ($) ft² member	Mar. 31, 2018 USD ($) a	Dec. 31, 2017 USD ($)	Sep. 30, 2013 USD ($)
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures		$ 30,098,000			$ 30,098,000	$ 30,031,000
Equity in earnings (loss)		167,000	$ 228,000
Equity		30,098,000			30,098,000	30,031,000
Debt		115,301,000			115,301,000	114,273,000
Promissory note agreement
Schedule of Equity Method Investments [Line Items]
Debt instrument face amount							$ 4,750,000
Line of Credit
Schedule of Equity Method Investments [Line Items]
Summarized financial information, maximum borrowing capacity		$ 52,000,000			$ 52,000,000
Petro Travel Plaza Holdings, LLC
Schedule of Equity Method Investments [Line Items]
Unconsolidated joint ventures, voting rights		50.00%
Unconsolidated joint ventures, ownership interest		60.00%			60.00%
Equity		$ 17,955,000			$ 17,955,000	17,422,000
Debt		15,280,000			15,280,000	15,280,000
Majestic Realty Co.
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures		$ 24,773,000			24,773,000
Number of joint venture contracts | joint_venture		2
Investment in unconsolidated joint ventures		$ 579,000			579,000
Area of building owned and leased | ft²		651,909
Majestic Realty Co. | Promissory note agreement
Schedule of Equity Method Investments [Line Items]
Debt instrument face amount		$ 21,080,000			21,080,000
TRC-MRC 2 LLC
Schedule of Equity Method Investments [Line Items]
Equity		0			0	0
Debt		(21,080,000)			(21,080,000)	21,080,000
Deficit balance		576,000			576,000
TRCC-East
Schedule of Equity Method Investments [Line Items]
Area of building owned and leased | ft²	480,480
Distribution of earnings from unconsolidated joint ventures					1,952,000
Deficit balance		3,000			3,000
Number of acres for development | ft²				326,000
TRC-MRC 1, LLC
Schedule of Equity Method Investments [Line Items]
Equity		0			0	0
Debt		21,080,000			21,080,000	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		$ 12,143,000			$ 12,143,000
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		$ 2,897,000			$ 2,897,000	2,802,000
Area of building owned and leased | ft²		606,000
Debt		$ 9,577,000			9,577,000	9,711,000
Lease renewal term		3 years
18-19 West, LLC
Schedule of Equity Method Investments [Line Items]
Equity		$ 1,769,000			1,769,000	1,782,000
Debt		$ 0			0	0
Number of acres for development | a		61.5
TRCC/Rock Outlet Center
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures				$ 87,000,000
Equity		$ 7,477,000			7,477,000	8,025,000
Debt		48,284,000			48,284,000	48,769,000
Construction loan percent of costs				60.00%
Equity contributions, percent				40.00%
Number of members | member				2
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%