Acquisitions (Additional Information) (Details)	Feb. 12, 2020 USD ($) ft² a	Sep. 30, 2020 USD ($) ft² property
Property, Plant and Equipment [Line Items]
Rentable square feet (in sq ft) | ft²		17,200,000
Percentage leased as of acquisition	95.00%	86.90%
$500 Million Unsecured 2018 Line of Credit | Unsecured Debt
Property, Plant and Equipment [Line Items]
Face amount of debt instrument		$ 500,000,000
Dallas Galleria Office Towers
Property, Plant and Equipment [Line Items]
Number of properties acquired | property		3
Ownership percentage acquired	100.00%
Rentable square feet (in sq ft) | ft²	1,435,466
Net contractual purchase price	$ 396,200,000
Area of land acquired (in acres) | a	1.9
Closing costs	$ 600,000