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 (Loss)	Retained Earnings (Loss) Series E Preferred Stock	Retained Earnings (Loss) Series F Preferred Stock	Accumulated Other Comprehensive Income (Loss)	Noncontrolling Interests
Balance at Dec. 31, 2017	$ 3,840,910			$ 3,840,593			$ 287,500	$ 345,000	$ 1,537	$ 3,599,475	$ (379,181)			$ (13,738)	$ 317
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	173,873			173,854							173,854				19
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	(140,207)			(140,207)					2	5,374	(145,583)
Issuance of common stock:
Director compensation	718			718						718
Stock purchase plan	217			217						217
ATM equity program	126,685			126,685					30	126,655
Issuance of shares of restricted common stock	(89)			(89)					2	(91)
Stock issuance costs	(1,754)			(1,754)						(1,754)
Amortization of deferred compensation	3,719			3,719						3,719
Amortization of interest rate hedges	1,056			1,056										1,056
Fair value of forward starting swaps	1,095			1,095										1,095
Valuation adjustments – available-for-sale securities	52			52										52
Sale of AFS	0
Balance at Jun. 30, 2018	3,989,111			3,988,775			287,500	345,000	1,571	3,734,313	(368,074)			(11,535)	336
Balance at Mar. 31, 2018	3,864,506			3,864,180			287,500	345,000	1,540	3,602,865	(357,216)			(15,509)	326
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	70,583			70,573							70,573				10
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	(69,019)			(69,019)					1	3,830	(72,850)
Issuance of common stock:
Director compensation	422			422						422
Stock purchase plan	119			119						119
ATM equity program	126,685			126,685					30	126,655
Stock issuance costs	(1,448)			(1,448)						(1,448)
Amortization of deferred compensation	1,870			1,870						1,870
Amortization of interest rate hedges	531			531										531
Fair value of forward starting swaps	3,259			3,259										3,259
Valuation adjustments – available-for-sale securities	184			184										184
Sale of AFS	0
Balance at Jun. 30, 2018	3,989,111			3,988,775			287,500	345,000	1,571	3,734,313	(368,074)			(11,535)	336
Balance 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
Issuance of shares of restricted common stock									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
Sale of AFS	(1,331)			(1,331)
Other	505			505										505
Distributions to noncontrolling interests	(776)														(776)
Balance at Jun. 30, 2019	4,222,451			4,222,449			287,500	345,000	1,636	4,042,318	(443,822)			(10,183)	2
Balance 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)
Sale of AFS	0
Distributions to noncontrolling interests	(776)														(776)
Balance at Jun. 30, 2019	$ 4,222,451			$ 4,222,449			$ 287,500	$ 345,000	$ 1,636	$ 4,042,318	$ (443,822)			$ (10,183)	$ 2