Transactions (Dispositions) (Details) - Disposed of by Sale - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 19, 2020	Jan. 16, 2020	Sep. 26, 2019	Apr. 15, 2019
Pasadena Corporate Park
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
% Sold	100.00%
Sales Price	$ 78,000
Gain (loss) on sale	$ (83)
Cranberry Woods Drive
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
% Sold			100.00%
Sales Price		$ 180,000	$ 180,000
Gain (loss) on sale		$ 13,400	$ 13,428
Lindbergh Center
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
% Sold				100.00%
Sales Price				$ 187,000
Gain (loss) on sale				$ 0
One & Three Glenlake Parkway
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
% Sold					100.00%
Sales Price					$ 227,500
Gain (loss) on sale					$ 42,030