Condensed Consolidated Statements of Equity (Unaudited) Statement - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Cumulative Net Income	Cumulative Dividends
Beginning balance at Dec. 31, 2018	$ 1,716,642	$ 1,253	$ 3,180,284	$ (902)	$ 1,088,119	$ (2,552,112)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of issuance costs	192,475	61	192,414
Common stock redemptions	(3,267)	(1)	(3,266)
Share-based compensation	10,141	1	10,140
Net income	11,975				11,975
Reclassification adjustments for losses included in net income (interest expense)	74			74
Losses arising during the period on interest rate swaps and treasury rate locks	(7,642)			(7,642)
Dividends to common stockholders (in usd per share)	(115,237)					(115,237)
Ending balance at Sep. 30, 2019	1,805,161	1,314	3,379,572	(8,470)	1,100,094	(2,667,349)
Beginning balance at Jun. 30, 2019	1,769,443	1,292	3,305,344	(6,189)	1,097,493	(2,628,497)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of issuance costs	71,814	22	71,792
Common stock redemptions	(2,695)		(2,695)
Share-based compensation	5,131		5,131
Net income	2,601				2,601
Reclassification adjustments for losses included in net income (interest expense)	60			60
Losses arising during the period on interest rate swaps and treasury rate locks	(2,341)			(2,341)
Dividends to common stockholders (in usd per share)	(38,852)					(38,852)
Ending balance at Sep. 30, 2019	1,805,161	1,314	3,379,572	(8,470)	1,100,094	(2,667,349)
Beginning balance at Dec. 31, 2019	1,900,009	1,347	3,485,003	(6,175)	1,127,304	(2,707,470)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of issuance costs	40,490	13	40,477
Common stock redemptions	(798)		(798)
Share-based compensation	7,449		7,448
Net income	88,058				88,058
Reclassification adjustments for losses included in net income (interest expense)	2,367			2,367
Losses arising during the period on interest rate swaps and treasury rate locks	(15,459)			(15,459)
Dividends to common stockholders (in usd per share)	(121,741)					(121,741)
Ending balance at Sep. 30, 2020	1,900,375	1,361	3,532,130	(19,267)	1,215,362	(2,829,211)
Beginning balance at Jun. 30, 2020	1,929,361	1,360	3,529,559	(20,294)	1,207,132	(2,788,396)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of issuance costs	127	1	126
Share-based compensation	2,445		2,445
Net income	8,230				8,230
Reclassification adjustments for losses included in net income (interest expense)	1,101			1,101
Losses arising during the period on interest rate swaps and treasury rate locks	(74)			(74)
Dividends to common stockholders (in usd per share)	(40,815)					(40,815)
Ending balance at Sep. 30, 2020	$ 1,900,375	$ 1,361	$ 3,532,130	$ (19,267)	$ 1,215,362	$ (2,829,211)