Investment in Unconsolidated and Consolidated Joint Ventures - Investment Information (Details)		1 Months Ended		3 Months Ended			6 Months Ended		12 Months Ended
	Apr. 01, 2019 USD ($)	Apr. 30, 2019 USD ($) ft²	Nov. 30, 2018 ft²	Dec. 31, 2019	Jun. 30, 2019 USD ($) a	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) a ft² joint_venture	Jun. 30, 2018 USD ($)	Dec. 31, 2013 ft²	Dec. 31, 2018 USD ($)	Jun. 01, 2018 USD ($)
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated joint ventures					$ 37,151,000		$ 37,151,000			$ 28,602,000
Equity in earnings (loss)					1,971,000	$ 652,000	2,847,000	$ 819,000
Equity					37,151,000		37,151,000			28,602,000
Debt					134,180,000		134,180,000			121,326,000
Value of land contributed							5,854,000	$ 0
Centennial
Schedule of Equity Method Investments [Line Items]
Noncontrolling interest balance					$ 11,039,000		$ 11,039,000			13,172,000
Consolidated joint venture, ownership interest					92.41%		92.41%
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					$ 21,902,000		$ 21,902,000			18,426,000
Debt					15,285,000		15,285,000			15,283,000
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							3
Area of building owned and leased | ft²							651,909
TRC-MRC 3, LLC
Schedule of Equity Method Investments [Line Items]
Equity					5,954,000		$ 5,954,000			0
Number of acres for development | ft²		579,040	579,040
Debt					14,588,000		14,588,000			0
Profit margin	$ 1,533,000	$ 1,500,000
Deferred profit margin	1,532,000	1,500,000
TRC-MRC 3, LLC | Land
Schedule of Equity Method Investments [Line Items]
Value of land contributed	$ 5,854,000	$ 5,900,000
TRC-MRC 3, LLC | Scenario, Forecast
Schedule of Equity Method Investments [Line Items]
Lease agreement, rentable space				67.00%
TRC-MRC 2, LLC
Schedule of Equity Method Investments [Line Items]
Equity					0		0			0
Debt					24,738,000		24,738,000			25,014,000
Debt instrument face amount											$ 25,240,000
Deficit balance					2,554,000		$ 2,554,000
TRCC-East
Schedule of Equity Method Investments [Line Items]
Number of acres for development | ft²									326,000
Area of building owned and leased | ft²							480,480
Deficit balance					261,000		$ 261,000
TRC-MRC 1, LLC
Schedule of Equity Method Investments [Line Items]
Equity					0		0			0
Debt					24,811,000		24,811,000			25,030,000
Construction Loan					25,030,000		$ 25,030,000
Rockefeller Joint Ventures
Schedule of Equity Method Investments [Line Items]
Number of joint venture contracts | joint_venture							3
Number of acres for development | a							91
Investment in unconsolidated joint ventures					$ 9,295,000		$ 9,295,000
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%		50.00%
Equity					$ 2,896,000		$ 2,896,000			2,691,000
Debt					8,903,000		$ 8,903,000			9,173,000
Area of building owned and leased | ft²							606,000
Option to extend, joint venture							3 years
18-19 West, LLC
Schedule of Equity Method Investments [Line Items]
Equity					1,756,000		$ 1,756,000			1,783,000
Debt					0		$ 0			0
Number of acres for development | a							63.5
TRCC/Rock Outlet Center, LLC
Schedule of Equity Method Investments [Line Items]
Equity					4,643,000		$ 4,643,000			5,702,000
Debt					45,855,000		45,855,000			$ 46,826,000
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