Acquisitions (Details) - Jun. 30, 2015	USD ($) a ft²
Business Acquisition [Line Items]
Ownership of properties acquired	100.00%
$500 Million Unsecured Line of Credit [Member] | Unsecured Debt [Member] | Line of Credit [Member]
Business Acquisition [Line Items]
Face amount of debt instrument	$ 500,000,000
Amount of line of credit	$ 500,000,000
Park Place on Turtle Creek [Member]
Business Acquisition [Line Items]
Rentable Square Feet | ft²	177,844
Percentage Leased as of Acquisition	88.00%
Purchase Price (in millions)	$ 46,600,000
Two Pierce Land Parcel [Member]
Business Acquisition [Line Items]
Purchase Price (in millions)	$ 3,700,000
Acreage | a	4.73