Consolidated Statements of Changes In Equity - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Cumulative Effect, Period of Adoption, Adjusted Balance	Common Stock	Common Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Paid-in Capital	Paid-in Capital Cumulative Effect, Period of Adoption, Adjusted Balance	Redeemable Perpetual Preferred  Stock	Redeemable Perpetual Preferred  Stock Cumulative Effect, Period of Adoption, Adjusted Balance	Distributions in Excess of Accumulated Earnings	Distributions in Excess of Accumulated Earnings Cumulative Effect, Period of Adoption, Adjustment	Distributions in Excess of Accumulated Earnings Cumulative Effect, Period of Adoption, Adjusted Balance	Accumulated Other Comprehensive Income (Loss)	Accumulated Other Comprehensive Income (Loss) Cumulative Effect, Period of Adoption, Adjusted Balance	Non- Controlling Interests – Common OP Units	Non- Controlling Interests – Common OP Units Cumulative Effect, Period of Adoption, Adjusted Balance
Beginning balance at Dec. 31, 2017	$ 1,100,042	$ (15,186)	$ 1,084,856	$ 1,766	$ 1,766	$ 1,241,226	$ 1,241,226	$ 0	$ 0	$ (211,980)	$ (15,186)	$ (227,166)	$ 942	$ 942	$ 68,088	$ 68,088
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exchange of Common OP Units for Common Stock	0			2		1,023									(1,025)
Issuance of Common Stock through exercise of options	3,823			4		3,819
Issuance of Common Stock through employee stock purchase plan	2,043					2,043
Issuance of Common Stock	78,755			20		78,735
Compensation expenses related to restricted stock and stock options	9,995					9,995
Repurchase of Common Stock or Common OP Units	(3,011)					(3,011)
Adjustment for Common OP Unitholders in the Operating Partnership	0					(3,684)									3,684
Adjustment for fair market value of swap	1,357												1,357
Consolidated net income	226,386							16		212,596					13,774
Distributions	(209,209)							(16)		(196,464)					(12,729)
Other	(1,651)					(1,651)
Ending balance at Dec. 31, 2018	1,193,344			1,792		1,328,495		0		(211,034)			2,299		71,792
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exchange of Common OP Units for Common Stock	0			10		6,539									(6,549)
Issuance of Common Stock through exercise of options	53					53
Issuance of Common Stock through employee stock purchase plan	2,429					2,429
Issuance of Common Stock	59,319			10		59,309
Compensation expenses related to restricted stock and stock options	10,481					10,481
Repurchase of Common Stock or Common OP Units	(53)					(53)
Adjustment for Common OP Unitholders in the Operating Partnership	0					(3,210)									3,210
Adjustment for fair market value of swap	(2,679)												(2,679)
Consolidated net income	295,922							16		279,123					16,783
Distributions	(235,581)							(16)		(222,407)					(13,158)
Other	(1,347)					(1,347)
Ending balance at Dec. 31, 2019	$ 1,321,888	$ (3,875)		1,812		1,402,696		0		(154,318)	$ (3,875)		(380)		72,078
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Accounting Standards Update [Extensible List]	us-gaap:AccountingStandardsUpdate201613Member
Exchange of Common OP Units for Common Stock	$ 0			1		81									(82)
Issuance of Common Stock through employee stock purchase plan	2,026					2,026
Compensation expenses related to restricted stock and stock options	11,527					11,527
Repurchase of Common Stock or Common OP Units	(3,962)					(3,962)
Adjustment for Common OP Unitholders in the Operating Partnership	0					(300)									300
Adjustment for fair market value of swap	380												380
Consolidated net income	241,416							16		228,268					13,132
Distributions	(263,974)							(16)		(249,598)					(14,360)
Other	(671)					(671)
Ending balance at Dec. 31, 2020	$ 1,304,755			$ 1,813		$ 1,411,397		$ 0		$ (179,523)			$ 0		$ 71,068