Consolidated Statements of Equity - USD ($)	Total	Common Stock	Additional Paid- in Capital	Common Shares Held in Deferred Compensation Plan	Deferred Compensation Plan	Retained Earnings	Accumulated Other Comprehensive Loss
Beginning balance at Dec. 31, 2019	$ 1,517,123,000	$ 673,000	$ 1,514,266,000			$ 2,621,000	$ (437,000)
Beginning balance (in shares) at Dec. 31, 2019		67,252,787
Increase (Decrease) in Stockholders' Equity
Net income	12,856,000					12,856,000
Issuance of common stock, net of issuance costs	$ 29,651,000	$ 4,000	29,647,000
Issuance of common stock, net of issuance costs (in shares)	427,027	562,521
Repurchase of common stock related to employee awards	$ (240,000)		(240,000)
Repurchase of common stock related to employee awards (in shares)		(4,510)
Issuance of restricted stock (in shares)		20,501
Stock-based compensation	1,573,000		1,573,000
Common stock dividends	(18,314,000)					(18,314,000)
Deposits to deferred compensation plan	0		7,346,000		$ (7,346,000)
Deposits to deferred compensation plan (in shares)		(135,494)		(135,494)
Other comprehensive income	73,000						73,000
Ending balance (in shares) at Mar. 31, 2020		67,695,805
Ending balance at Mar. 31, 2020	1,542,722,000	$ 677,000	1,552,592,000		(7,346,000)	(2,837,000)	(364,000)
Beginning balance at Dec. 31, 2020	1,588,184,000	$ 686,000	1,589,301,000	$ 139,224	(7,546,000)	5,926,000	(183,000)
Beginning balance (in shares) at Dec. 31, 2020		68,376,364
Increase (Decrease) in Stockholders' Equity
Net income	16,257,000					16,257,000
Issuance of common stock, net of issuance costs	47,873,000	$ 7,000	47,866,000
Issuance of common stock, net of issuance costs (in shares)		837,846
Repurchase of common stock related to employee awards	(582,000)		(582,000)
Repurchase of common stock related to employee awards (in shares)		(6,534)
Issuance of restricted stock (in shares)		25,654
Stock-based compensation	1,970,000		1,970,000
Common stock dividends	(20,091,000)					(20,091,000)
Deposits to deferred compensation plan	0		7,321,000		(7,321,000)
Deposits to deferred compensation plan (in shares)		(131,322)		(131,322)
Other comprehensive income	106,000						106,000
Ending balance (in shares) at Mar. 31, 2021		69,102,008
Ending balance at Mar. 31, 2021	$ 1,633,717,000	$ 693,000	$ 1,645,876,000	$ 270,546	$ (14,867,000)	$ 2,092,000	$ (77,000)