Condensed Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Treasury Stock	Distributions in Excess of Net Income	Stockholders’ Investment	Nonredeemable Noncontrolling Interests
Beginning balance at Dec. 31, 2015	$ 1,683,415		$ 220,256	$ 1,722,224	$ (134,630)	$ (124,435)	$ 1,683,415	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,796					22,796	22,796
Common stock issued pursuant to:
Stock based compensation	(427)		180	(607)			(427)
Amortization of stock options and restricted stock, net of forfeitures	403			403			403
Contributions from nonredeemable noncontrolling interest	758							758
Repurchase of common stock	(13,743)				(13,743)		(13,743)
Common dividends	(16,918)					(16,918)	(16,918)
Ending balance at Mar. 31, 2016	1,676,284		220,436	1,722,020	(148,373)	(118,557)	1,675,526	758
Beginning balance at Dec. 31, 2016	2,514,240	$ 6,867	403,747	3,407,430	(148,373)	(1,214,114)	2,455,557	58,683
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	4,858					4,751	4,751	107
Common stock issued pursuant to:
Common stock offering, net of issuance costs	211,825		25,000	186,825			211,825
Stock based compensation	(701)		231	(932)			(701)
Spin-off of Parkway, Inc.	404					404	404
Common stock redemption by unit holders	0		251	1,766			2,017	(2,017)
Amortization of stock options and restricted stock, net of forfeitures	489		(3)	492			489
Contributions from nonredeemable noncontrolling interest	630							630
Distributions to nonredeemable noncontrolling interest	(491)							(491)
Common dividends	(48,738)					(48,738)	(48,738)
Ending balance at Mar. 31, 2017	$ 2,682,516	$ 6,867	$ 429,226	$ 3,595,581	$ (148,373)	$ (1,257,697)	$ 2,625,604	$ 56,912