CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Series E Preferred Stock	Series F Preferred Stock	Total  Stockholders’ Equity	Total  Stockholders’ Equity Series E Preferred Stock	Total  Stockholders’ Equity Series F Preferred Stock	Preferred Stock Series E Preferred Stock	Preferred Stock Series F Preferred Stock	Common Stock	Capital in Excess of Par Value	Retained Earnings (Deficit)	Retained Earnings (Deficit) Series E Preferred Stock	Retained Earnings (Deficit) Series F Preferred Stock	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Balances at Dec. 31, 2018	$ 4,154,605			$ 4,154,250			$ 287,500	$ 345,000	$ 1,616	$ 3,950,055	$ (424,225)			$ (5,696)	$ 355
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	159,124			158,701							158,701				423
Dividends declared and paid:
Preferred stock dividends declared and paid		$ (8,194)	$ (8,970)		$ (8,194)	$ (8,970)						$ (8,194)	$ (8,970)
Common stock dividends declared and paid	(154,688)			(154,688)					2	6,949	(161,639)
Issuance of common stock:
Director compensation	643			643						643
Stock purchase plan	216			216						216
ATM equity program	80,812			80,812					15	80,797
Restricted shares, net of forfeitures	0								3	(3)
Stock issuance costs	(766)			(766)						(766)
Amortization of deferred compensation	4,427			4,427						4,427
Amortization of interest rate hedges	648			648										648
Fair value of forward starting swaps	(3,920)			(3,920)										(3,920)
Valuation adjustments – available-for-sale securities	116			116										116
Realized gain – available-for-sale securities	(1,331)			(1,331)										(1,331)
Other	505			505							505
Distributions to noncontrolling interests	(776)														(776)
Balances at Jun. 30, 2019	4,222,451			4,222,449			287,500	345,000	1,636	4,042,318	(443,822)			(10,183)	2
Balances at Mar. 31, 2019	4,152,887			4,152,522			287,500	345,000	1,620	3,957,835	(432,845)			(6,588)	365
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	79,091			78,678							78,678				413
Dividends declared and paid:
Preferred stock dividends declared and paid		$ (4,096)	(4,485)		$ (4,096)	(4,485)						$ (4,096)	(4,485)
Common stock dividends declared and paid	(79,283)			(79,283)					1	1,790	(81,074)
Issuance of common stock:
Director compensation	321			321						321
Stock purchase plan	97			97						97
ATM equity program	80,812			80,812					15	80,797
Stock issuance costs	(724)			(724)						(724)
Amortization of deferred compensation	2,202			2,202						2,202
Amortization of interest rate hedges	325			325										325
Fair value of forward starting swaps	(3,920)			(3,920)										(3,920)
Valuation adjustments – available-for-sale securities	0
Realized gain – available-for-sale securities	0
Distributions to noncontrolling interests	(776)														(776)
Balances at Jun. 30, 2019	4,222,451			4,222,449			$ 287,500	345,000	1,636	4,042,318	(443,822)			(10,183)	2
Balances at Dec. 31, 2019	4,331,682			4,331,675				345,000	1,718	4,495,314	(499,229)			(11,128)	7
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	111,441			111,443											(2)
Dividends declared and paid:
Preferred stock dividends declared and paid			(8,970)			(8,970)							(8,970)
Common stock dividends declared and paid	(175,267)			(175,267)						1,151	(176,418)
Issuance of common stock:
Director compensation	596			596						596
Stock purchase plan	170			170						170
ATM equity program	52,763			52,763					14	52,749
Restricted shares, net of forfeitures									3	(3)
Stock issuance costs	(746)			(746)						(746)
Amortization of deferred compensation	5,727			5,727						5,727
Amortization of interest rate hedges	1,021			1,021										1,021
Fair value of forward starting swaps	(7,617)			(7,617)										(7,617)
Valuation adjustments – available-for-sale securities	0
Realized gain – available-for-sale securities	0
Balances at Jun. 30, 2020	4,310,800			4,310,795				345,000	1,735	4,554,958	(573,174)			(17,724)	5
Balances at Mar. 31, 2020	4,300,935			4,300,930				345,000	1,721	4,499,255	(526,684)			(18,362)	5
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	46,265			46,265							46,265
Dividends declared and paid:
Preferred stock dividends declared and paid			$ (4,485)			$ (4,485)							$ (4,485)
Common stock dividends declared and paid	(87,739)			(87,739)						531	(88,270)
Issuance of common stock:
Director compensation	298			298						298
Stock purchase plan	94			94						94
ATM equity program	52,763			52,763					14	52,749
Stock issuance costs	(746)			(746)						(746)
Amortization of deferred compensation	2,777			2,777						2,777
Amortization of interest rate hedges	638			638										638
Fair value of forward starting swaps	0
Valuation adjustments – available-for-sale securities	0
Realized gain – available-for-sale securities	0
Balances at Jun. 30, 2020	$ 4,310,800			$ 4,310,795				$ 345,000	$ 1,735	$ 4,554,958	$ (573,174)			$ (17,724)	$ 5