Investment in Unconsolidated and Consolidated Joint Ventures - Investment Information (Details)	1 Months Ended		3 Months Ended			6 Months Ended
	Sep. 30, 2016 ft²	Aug. 31, 2016 USD ($) ft²	Jun. 30, 2017 USD ($) a	Jun. 30, 2016 USD ($)	Jun. 30, 2013 USD ($) ft² member	Jun. 30, 2017 USD ($) a ft² joint_venture	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2013 USD ($)
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures			$ 34,505,000			$ 34,505,000		$ 33,803,000
Equity in earnings (loss)			1,560,000	$ 1,842,000		1,788,000	$ 3,297,000
Equity			34,505,000			34,505,000		33,803,000
Debt			104,649,000			104,649,000		97,318,000
Distributions from joint venture						1,952,000
Distributions in Excess of Investment in Unconsolidated Joint Venture			4,000			4,000
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			$ 21,086,000			$ 21,086,000		18,372,000
Debt			15,277,000			$ 15,277,000		15,275,000
Majestic Realty Co.
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures		$ 24,773,000
Number of joint venture contracts | joint_venture						2
Investment in unconsolidated joint ventures			422,000			$ 422,000
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
TRC-MRC 2 LLC
Schedule of Equity Method Investments [Line Items]
Equity			422,000			422,000		1,431,000
Debt			21,080,000			$ 21,080,000		21,080,000
Rockefeller Joint Ventures
Schedule of Equity Method Investments [Line Items]
Number of joint venture contracts | joint_venture						3
Investment in unconsolidated joint ventures			$ 12,994,000			$ 12,994,000
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
Schedule of Equity Method Investments [Line Items]
Unconsolidated joint ventures, ownership interest			50.00%			50.00%
Equity			$ 2,600,000			$ 2,600,000		2,837,000
Area of building owned and leased | ft²						606,000
Debt			$ 9,981,000			$ 9,981,000		10,251,000
18-19 West LLC
Schedule of Equity Method Investments [Line Items]
Unconsolidated joint ventures, ownership interest			50.00%			50.00%
Equity			$ 1,745,000			$ 1,745,000		1,741,000
Debt			0			$ 0		0
Number of acres for development | a						61.5
TRCC-East
Schedule of Equity Method Investments [Line Items]
Area of building owned and leased | ft²	480,480
Number of acres for development | ft²					326,000
TRC-MRC 1 LLC
Schedule of Equity Method Investments [Line Items]
Equity			0			$ 0		224,000
Debt			8,570,000			8,570,000		0
TRCC/Rock Outlet Center
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures					$ 87,000,000
Equity			8,652,000			8,652,000		9,198,000
Debt			$ 49,741,000			$ 49,741,000		50,712,000
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
Consolidated joint venture, ownership interest			85.95%			85.95%