Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Additional Paid-In Capital	Treasury Stock	Distributions in Excess of Cumulative Net Income	Stockholders’ Investment	Nonredeemable Noncontrolling Interests
Beginning balance at Dec. 31, 2014	$ 1,673,458	$ 0	$ 220,083	$ 1,720,972	$ (86,840)	$ (180,757)	$ 1,673,458	$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	125,629					125,518	125,518	111
Common stock issued pursuant to stock based -- compensation	(72)		173	(245)			(72)
Amortization of stock options and restricted stock, net of forfeitures	1,473			1,473			1,473
Distributions to nonredeemable noncontrolling interests	(111)							(111)
Repurchase of common stock	(47,790)				(47,790)		(47,790)
Common dividends	(69,196)					(69,196)	(69,196)
Other	24			24			24
Ending balance at Dec. 31, 2015	1,683,415	0	220,256	1,722,224	(134,630)	(124,435)	1,683,415	0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	80,104					79,109	79,109	995
Securities issued in merger	1,950,008	6,867	183,207	1,683,076			1,873,150	76,858
Noncontrolling interest in assets acquired in merger	292,337							292,337
Common stock issued pursuant to stock based -- compensation	504		280	224			504
Spin-off of New Parkway	(1,141,061)					(1,118,240)	(1,118,240)	(22,821)
Amortization of stock options and restricted stock, net of forfeitures	1,648		(35)	1,683			1,648
Common stock redemption by unit holders	0		39	223			262	(262)
Contributions from nonredeemable noncontrolling interests	4,126							4,126
Distributions to nonredeemable noncontrolling interests	(292,550)							(292,550)
Repurchase of common stock	(13,743)				(13,743)		(13,743)
Common dividends	(50,548)					(50,548)	(50,548)
Ending 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	219,959					216,275	216,275	3,684
Common stock offering, net of issuance costs	211,774		25,000	186,774			211,774
Common stock issued pursuant to stock based -- compensation	124		403	(279)			124
Spin-off of New Parkway	545					545	545
Amortization of stock options and restricted stock, net of forfeitures	1,983		(3)	1,986			1,983
Common stock redemption by unit holders	0		1,203	8,865			10,068	(10,068)
Contributions from nonredeemable noncontrolling interests	2,646							2,646
Distributions to nonredeemable noncontrolling interests	(1,807)							(1,807)
Common dividends	(124,353)					(124,353)	(124,353)
Ending balance at Dec. 31, 2017	$ 2,825,111	$ 6,867	$ 430,350	$ 3,604,776	$ (148,373)	$ (1,121,647)	$ 2,771,973	$ 53,138