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	103,289			103,280							103,280				9
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	(71,188)			(71,188)					1	1,544	(72,733)
Issuance of common stock:
Director compensation and other	296			296						296
Stock purchase plan	98			98						98
Issuance of shares of restricted common stock	(89)			(89)					2	(91)
Stock issuance costs	(306)			(306)						(306)
Amortization of deferred compensation	1,849			1,849						1,849
Amortization of interest rate hedges	525			525										525
Fair value of forward starting swaps	(2,164)			(2,164)										(2,164)
Valuation adjustments – available-for-sale securities	(132)			(132)										(132)
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
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	80,033			80,023							80,023				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	(75,406)			(75,406)					1	5,159	(80,566)
Issuance of common stock:
Director compensation and other	322			322						322
Stock purchase plan	119			119						119
Issuance of shares of restricted common stock	0			0					3	(3)
Stock issuance costs	(42)			(42)						(42)
Amortization of deferred compensation	2,225			2,225						2,225
Amortization of interest rate hedges	323			323										323
Fair value of forward starting swaps	0
Valuation adjustments – available-for-sale securities	116			116										116
Realized gain – available-for-sale securities	(1,331)			(1,331)										(1,331)
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