Consolidated Statements of Equity - USD ($)	Total	Common Stock	Additional Paid-in Capital	Common Stock Held At Rabbi Trust	Deferred Compensation, Share-based Payments	Retained Earnings	Accumulated Other Comprehensive (Loss) Income
Beginning balance (in shares) at Dec. 31, 2017		55,368,737
Beginning balance at Dec. 31, 2017	$ 1,027,494,000	$ 553,000	$ 1,023,184,000			$ 4,803,000	$ (1,046,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	63,289,000					63,289,000
Issuance of common stock, net of issuance costs (in shares)		(5,698,326)
Issuance of common stock, net of issuance costs	212,221,000	$ 57,000	212,164,000
Repurchase of common stock (in shares)		(107,267)
Issuance of restricted stock (in shares)		53,915
Repurchase of common stock related to employee awards	(3,870,000)		(3,870,000)
Stock-based compensation	2,285,000		2,285,000
Common stock dividends	(53,907,000)					(53,907,000)
Other comprehensive income	285,000						285,000
Ending balance (in shares) at Dec. 31, 2018		61,013,711
Ending balance at Dec. 31, 2018	1,247,797,000	$ 610,000	1,233,763,000			14,185,000	(761,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 55,516,000					55,516,000
Issuance of common stock, net of issuance costs (in shares)	(6,064,576)	(6,271,863)
Issuance of common stock, net of issuance costs	$ 280,499,000	$ 63,000	280,436,000
Repurchase of common stock (in shares)		(143,886)
Issuance of restricted stock (in shares)		111,099
Repurchase of common stock related to employee awards	(3,959,000)		(3,959,000)
Stock-based compensation	4,026,000		4,026,000
Common stock dividends	(67,080,000)					(67,080,000)
Other comprehensive income	324,000						324,000
Ending balance (in shares) at Dec. 31, 2019		67,252,787
Ending balance at Dec. 31, 2019	1,517,123,000	$ 673,000	1,514,266,000			2,621,000	(437,000)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	79,795,000					79,795,000
Issuance of common stock, net of issuance costs (in shares)		(1,344,281)
Issuance of common stock, net of issuance costs	70,651,000	$ 13,000	70,638,000
Repurchase of common stock (in shares)		(154,375)
Forfeiture of common stock related to employee awards (in shares)		(5,146)
Forfeiture of common stock related to employee awards	(265,000)		(265,000)
Issuance of restricted stock (in shares)		78,041
Repurchase of common stock related to employee awards	(9,572,000)		(9,572,000)
Stock-based compensation	6,688,000		6,688,000
Common stock dividends	(76,490,000)					(76,490,000)
Deposits to deferred compensation plan (in shares)		139,224		139,224,000
Deposits to deferred compensation plan	0		7,546,000		$ (7,546,000)
Other comprehensive income	254,000						254,000
Ending balance (in shares) at Dec. 31, 2020		68,376,364
Ending balance at Dec. 31, 2020	$ 1,588,184,000	$ 686,000	$ 1,589,301,000	$ 139,224,000	$ (7,546,000)	$ 5,926,000	$ (183,000)