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	30,561					30,561	30,561
Common stock issued pursuant to:
Stock based compensation	339		258	81			339
Amortization of stock options and restricted stock, net of forfeitures	813		(13)	826			813
Contributions from nonredeemable noncontrolling interest	1,473							1,473
Repurchase of common stock	(13,743)				(13,743)		(13,743)
Common dividends	(33,728)					(33,728)	(33,728)
Ending balance at Jun. 30, 2016	1,669,130		220,501	1,723,131	(148,373)	(127,602)	1,667,657	1,473
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	175,803					172,840	172,840	2,963
Common stock issued pursuant to:
Common stock offering, net of issuance costs	211,820		25,000	186,820			211,820
Director stock grants	1,010		121	889			1,010
Stock based compensation	(711)		232	(943)			(711)
Spin-off of Parkway, Inc.	562					562	562
Common stock redemption by unit holders	0		1,203	8,865			10,068	(10,068)
Amortization of stock options and restricted stock, net of forfeitures	969		(6)	975			969
Contributions from nonredeemable noncontrolling interest	900							900
Distributions to nonredeemable noncontrolling interest	(966)							(966)
Common dividends	(73,950)					(73,950)	(73,950)
Ending balance at Jun. 30, 2017	$ 2,829,677	$ 6,867	$ 430,297	$ 3,604,036	$ (148,373)	$ (1,114,662)	$ 2,778,165	$ 51,512