Investment in Unconsolidated Joint Ventures (Cousins W Rio Salado, LLC) (Details) ft² in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) ft²	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Schedule of Equity Method Investments [Line Items]
Income from unconsolidated joint ventures	$ 47,115	$ 10,562	$ 8,302
111 West Rio
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage	74.60%
Square footage of real estate property (square feet) | ft²	225
Income from unconsolidated joint ventures	$ 3,500
111 West Rio | American Airlines
Schedule of Equity Method Investments [Line Items]
Ownership interest percentage	25.40%
Purchase of interest in the building	$ 19,600