Transactions With Parkway Properties, Inc. (Discontinued Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Income from discontinued operations	$ 0	$ 19,163	$ 31,848
Loss on sale of discontinued operations, net	$ 0	0	(551)
Spin-off
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Rental property revenues		136,927	176,828
Rental property operating expenses		(58,336)	(73,630)
Other revenues		288	450
Interest expense		(6,022)	(7,988)
Depreciation and amortization		(47,345)	(63,791)
Other expenses		(6,349)	(21)
Income from discontinued operations		19,163	31,848
Loss on sale of discontinued operations, net		0	(551)
Cash provided by operating activities		42,604	76,395
Cash used in investing activities		$ (30,067)	$ (55,085)