CONDENSED CONSOLIDATED STATEMENTS OF EQUITY - USD ($) $ in Thousands	Total	Series E Preferred Stock	Series F Preferred Stock	ATM equity program	Total Stockholders’ Equity	Total Stockholders’ Equity Series E Preferred Stock	Total Stockholders’ Equity Series F Preferred Stock	Total Stockholders’ Equity ATM equity program	Preferred Stock Series E Preferred Stock	Preferred Stock Series F Preferred Stock	Common Stock	Common Stock ATM equity program	Capital in Excess of Par Value	Capital in Excess of Par Value ATM equity program	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	255,915				255,886										255,886				29
Dividends declared and paid:
Preferred stock dividends declared and paid		$ (12,291)	$ (13,455)			$ (12,291)	$ (13,455)									$ (12,291)	$ (13,455)
Common stock dividends declared and paid	(214,948)				(214,948)						3		8,885		(223,836)
Issuance of common stock:
Director compensation	1,047				1,047								1,047
Stock purchase plan	349				349								349
ATM equity program and equity offering				$ 211,372				$ 211,372				$ 49		$ 211,323
Restricted shares, net of buyback and surrender	(89)				(89)						2		(91)
Stock issuance costs	(2,914)				(2,914)								(2,914)
Amortization of deferred compensation	5,598				5,598								5,598
Amortization of interest rate hedges	1,581				1,581													1,581
Fair value of forward starting swaps	4,080				4,080													4,080
Valuation adjustments – available-for-sale securities	65				65													65
Realized gain – available-for-sale securities	0
Balance at Sep. 30, 2018	4,077,220				4,076,874				287,500	345,000	1,591		3,823,672		(372,877)			(8,012)	346
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	82,042				82,032										82,032				10
Dividends declared and paid:
Preferred stock dividends declared and paid		(4,097)	(4,485)			(4,097)	(4,485)									(4,097)	(4,485)
Common stock dividends declared and paid	(74,741)				(74,741)						1		3,511		(78,253)
Issuance of common stock:
Director compensation	329				329								329
Stock purchase plan	132				132								132
ATM equity program and equity offering				84,687				84,687				19		84,668
Stock issuance costs	(1,160)				(1,160)								(1,160)
Amortization of deferred compensation	1,879				1,879								1,879
Amortization of interest rate hedges	525				525													525
Fair value of forward starting swaps	2,985				2,985													2,985
Valuation adjustments – available-for-sale securities	13				13													13
Realized gain – available-for-sale securities	0
Balance at Sep. 30, 2018	4,077,220				4,076,874				287,500	345,000	1,591		3,823,672		(372,877)			(8,012)	346
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	225,822				225,394										225,394				428
Dividends declared and paid:
Preferred stock dividends declared and paid		(12,291)	(13,455)			(12,291)	(13,455)									(12,291)	(13,455)
Common stock dividends declared and paid	(229,403)				(229,403)						3		16,168		(245,574)
Issuance of common stock:
Director compensation	968				968								968
Stock purchase plan	309				309								309
ATM equity program and equity offering	395,500			127,337	395,500			127,337			70	24	395,430	127,313
Restricted shares, net of buyback and surrender											4		(4)
Stock issuance costs	(17,480)				(17,480)								(17,480)
Amortization of deferred compensation	6,841				6,841								6,841
Amortization of interest rate hedges	975				975													975
Fair value of forward starting swaps	(11,738)				(11,738)													(11,738)
Valuation adjustments – available-for-sale securities	116				116													116
Realized gain – available-for-sale securities	(1,331)				(1,331)
Other	505				505													505
Distributions to noncontrolling interests	(776)																		(776)
Balance at Sep. 30, 2019	4,626,504				4,626,497				287,500	345,000	1,717		4,479,600		(469,646)			(17,674)	7
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
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net earnings	66,698				66,693										66,693				5
Dividends declared and paid:
Preferred stock dividends declared and paid		$ (4,097)	$ (4,485)			$ (4,097)	$ (4,485)									$ (4,097)	$ (4,485)
Common stock dividends declared and paid	(74,715)				(74,715)						1		9,219		(83,935)
Issuance of common stock:
Director compensation	325				325								325
Stock purchase plan	94				94						1		93
ATM equity program and equity offering	395,500			$ 46,524	395,500			$ 46,524			70	$ 8	395,430	$ 46,516
Restricted shares, net of buyback and surrender											1		(1)
Stock issuance costs	(16,714)				(16,714)								(16,714)
Amortization of deferred compensation	2,414				2,414								2,414
Amortization of interest rate hedges	327				327													327
Fair value of forward starting swaps	(7,818)				(7,818)													(7,818)
Realized gain – available-for-sale securities	0
Balance at Sep. 30, 2019	$ 4,626,504				$ 4,626,497				$ 287,500	$ 345,000	$ 1,717		$ 4,479,600		$ (469,646)			$ (17,674)	$ 7