Consolidated Statements of Changes In Equity - USD ($) $ in Thousands	Total	Common Stock	Paid-in Capital	Distributions in Excess of Accumulated Earnings	Accumulated Other Comprehensive Income (Loss)	Non-controlling interests – Common OP Units
Beginning balance at Dec. 31, 2018	$ 1,193,344	$ 1,792	$ 1,328,495	$ (211,034)	$ 2,299	$ 71,792
Increase (Decrease) in Stockholders' Equity
Exchange of Common OP Units for Common Stock	0		66			(66)
Issuance of Common Stock through exercise of options	53		53
Issuance of Common Stock through employee stock purchase plan	652		652
Compensation expenses related to restricted stock and stock options	2,420		2,420
Repurchase of Common Stock or Common OP Units	(53)		(53)
Adjustment for Common OP Unitholders in the Operating Partnership	0		(56)			56
Adjustment for fair market value of swap	(931)				(931)
Consolidated net income	120,535			113,309		7,226
Distributions	(58,639)			(55,123)		(3,516)
Other	(63)		(63)
Ending balance at Mar. 31, 2019	1,257,318	1,792	1,331,514	(152,848)	1,368	75,492
Beginning balance at Dec. 31, 2019	1,321,888	1,812	1,402,696	(154,318)	(380)	72,078
Increase (Decrease) in Stockholders' Equity
Adjustment for fair market value of swap	(1,333)
Ending balance at Mar. 31, 2020	1,320,907	1,812	1,402,514	(153,703)	(1,713)	71,997
Increase (Decrease) in Stockholders' Equity
Cumulative effect of change in accounting principle (ASU 2016-13, Financial Instruments - Credit Losses (Topic 326))	(3,875)			(3,875)
Beginning balance at Jan. 01, 2020	1,318,013	1,812	1,402,696	(158,193)	(380)	72,078
Increase (Decrease) in Stockholders' Equity
Exchange of Common OP Units for Common Stock	0		63			(63)
Issuance of Common Stock through employee stock purchase plan	619		619
Compensation expenses related to restricted stock and stock options	2,964		2,964
Repurchase of Common Stock or Common OP Units	(3,962)		(3,962)
Adjustment for Common OP Unitholders in the Operating Partnership	0		277			(277)
Adjustment for fair market value of swap	(1,333)				(1,333)
Consolidated net income	70,724			66,875		3,849
Distributions	(65,975)			(62,385)		(3,590)
Other	(143)		(143)
Ending balance at Mar. 31, 2020	$ 1,320,907	$ 1,812	$ 1,402,514	$ (153,703)	$ (1,713)	$ 71,997