Consolidated Statement of Changes In Equity (Unaudited) - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Distributions in Excess of Accumulated Earnings	Non- controlling interests – Common OP Units	Accumulated Other Comprehensive Loss/(Income)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle	$ (15,186)			$ (15,186)
Adjusted balance	1,084,856	$ 883	$ 1,242,109	(227,166)	$ 68,088	$ 942
Balance at Dec. 31, 2017	1,100,042	883	1,242,109	(211,980)	68,088	942
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Conversion of Common OP Units to Common Stock		0	80		(80)
Issuance of Common Stock through employee stock purchase plan	503		503
Compensation expenses related to restricted stock and stock options	1,800		1,800
Adjustment for Common OP Unitholders in the Operating Partnership	0		782		(782)
Adjustment for fair market value of swap	1,873					1,873
Net income	64,177			60,222	3,955
Distributions	(52,010)			(48,805)	(3,205)
Other	(60)		(60)	0
Balance at Mar. 31, 2018	$ 1,101,139	$ 883	$ 1,245,214	$ (215,749)	$ 67,976	$ 2,815