CONSOLIDATED STATEMENTS OF CHANGES IN EQUITY - USD ($)	Total	Common Stock	Additional Paid-in Capital	Distributions In Excess Of Earnings	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interest in Joint Ventures
BALANCE at Dec. 31, 2016	$ 641,866,000	$ 3,000	$ 949,318,000	$ (313,655,000)	$ 1,995,000	$ 4,205,000
Comprehensive income
Net income	83,589,000	0	0	83,183,000	0	406,000
Net unrealized change in fair value of interest rate swaps - cash flow hedges	3,353,000	0	0	0	3,353,000	0
Common dividends declared - $2.52, $2.72, and $2.94 per share in 2017, 2018 and 2019, respectively	(86,560,000)	0	0	(86,560,000)	0	0
Stock-based compensation, net of forfeitures	7,012,000	0	7,012,000	0	0	0
Issuance of 1,370,457, 1,706,474, and 2,388,342 shares of common stock, common stock offering, net of expenses in 2017, 2018 and 2019, respectively	109,207,000	0	109,207,000	0	0	0
Issuance of 2,744, 1,844, and 1,893 shares of common stock, dividend reinvestment plan in 2017, 2018 and 2019, respectively	228,000	0	228,000	0	0	0
Withheld 33,695, 23,824, and 28,955 shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock in 2017, 2018 and 2019, respectively	(2,505,000)	0	(2,505,000)	0	0	0
Purchase of noncontrolling interest in joint venture	(4,704,000)	0	(2,107,000)	0	0	(2,597,000)
Distributions to noncontrolling interest	(478,000)	0	0	0	0	(478,000)
Contributions from noncontrolling interest	122,000	0	0	0	0	122,000
BALANCE at Dec. 31, 2017	751,130,000	3,000	1,061,153,000	(317,032,000)	5,348,000	1,658,000
Comprehensive income
Net income	88,636,000	0	0	88,506,000	0	130,000
Net unrealized change in fair value of interest rate swaps - cash flow hedges	1,353,000	0	0	0	1,353,000	0
Common dividends declared - $2.52, $2.72, and $2.94 per share in 2017, 2018 and 2019, respectively	(97,667,000)	0	0	(97,667,000)	0	0
Stock-based compensation, net of forfeitures	6,103,000	0	6,103,000	0	0	0
Issuance of 1,370,457, 1,706,474, and 2,388,342 shares of common stock, common stock offering, net of expenses in 2017, 2018 and 2019, respectively	157,319,000	1,000	157,318,000	0	0	0
Issuance of 2,744, 1,844, and 1,893 shares of common stock, dividend reinvestment plan in 2017, 2018 and 2019, respectively	164,000	0	164,000	0	0	0
Withheld 33,695, 23,824, and 28,955 shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock in 2017, 2018 and 2019, respectively	(2,055,000)	0	(2,055,000)	0	0	0
Purchase of noncontrolling interest in joint venture	(136,000)	0	(136,000)	0	0	0
Distributions to noncontrolling interest	(194,000)	0	0	0	0	(194,000)
Contributions from noncontrolling interest	50,000	0	0	0	0	50,000
BALANCE at Dec. 31, 2018	904,703,000	4,000	1,222,547,000	(326,193,000)	6,701,000	1,644,000
Comprehensive income
Net income	123,340,000	0	0	121,662,000	0	1,678,000
Net unrealized change in fair value of interest rate swaps - cash flow hedges	(3,894,000)	0	0	0	(3,894,000)	0
Common dividends declared - $2.52, $2.72, and $2.94 per share in 2017, 2018 and 2019, respectively	(111,771,000)	0	0	(111,771,000)	0	0
Stock-based compensation, net of forfeitures	9,374,000	0	9,374,000	0	0	0
Issuance of 1,370,457, 1,706,474, and 2,388,342 shares of common stock, common stock offering, net of expenses in 2017, 2018 and 2019, respectively	284,710,000	0	284,710,000	0	0	0
Issuance of 2,744, 1,844, and 1,893 shares of common stock, dividend reinvestment plan in 2017, 2018 and 2019, respectively	212,000	0	212,000	0	0	0
Withheld 33,695, 23,824, and 28,955 shares of common stock to satisfy tax withholding obligations in connection with the vesting of restricted stock in 2017, 2018 and 2019, respectively	(2,788,000)	0	(2,788,000)	0	0	0
Contributions from noncontrolling interest in joint ventures	821,000	0	0	0	0	821,000
Distributions to noncontrolling interest	(2,378,000)	0	0	0	0	(2,378,000)
BALANCE at Dec. 31, 2019	$ 1,202,329,000	$ 4,000	$ 1,514,055,000	$ (316,302,000)	$ 2,807,000	$ 1,765,000