Consolidated Statements of Equity - USD ($) $ in Thousands	Total	Preferred Stock	Common Stock	Capital in Excess of Par Value	Treasury Stock	Cumulative Net Income	Cumulative Dividends	Accumulated Other Comprehensive Income (loss)	Other Equity	Noncontrolling Interests
Balances at beginning of period at Dec. 31, 2016	$ 15,281,472	$ 1,006,250	$ 363,071	$ 16,999,691	$ (54,741)	$ 4,803,575	$ (8,144,981)	$ (169,531)	$ 3,059	$ 475,079
Comprehensive income:
Net income (loss)	543,593					522,774				20,819
Other comprehensive income (loss)	80,414							58,066		22,348
Total comprehensive income	624,007
Increase in noncontrolling interests				13,473
Decrease in noncontrolling interests	(2,468)									(15,941)
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	9,690		402	21,494	(9,807)				(2,399)
Net proceeds from issuance of common stock	621,436		8,881	612,555
Redemption of equity membership units	5,545		91	5,465	(11)
Redemption of preferred stock	(287,509)	(287,500)		9,760		(9,769)
Conversion of preferred stock		(247)	4	243
Option compensation expense	10								10
Dividends paid:
Common stock dividends	(1,277,321)						(1,277,321)
Preferred stock dividends	(49,410)						(49,410)
Balances at end of period at Dec. 31, 2017	14,925,452	718,503	372,449	17,662,681	(64,559)	5,316,580	(9,471,712)	(111,465)	670	502,305
Comprehensive income:
Net income (loss)	830,019					804,954				25,065
Other comprehensive income (loss)	(41,288)							(18,304)		(22,984)
Total comprehensive income	788,731
Increase in noncontrolling interests	406,778									449,879
Decrease in noncontrolling interests				(43,101)
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	24,149		188	28,277	(3,940)				(376)
Net proceeds from issuance of common stock	788,334		11,828	776,506
Conversion of preferred stock		(5)		5
Dividends paid:
Common stock dividends	(1,300,141)						(1,300,141)
Preferred stock dividends	(46,704)						(46,704)
Balances at end of period at Dec. 31, 2018	15,586,599	718,498	384,465	18,424,368	(68,499)	6,121,534	(10,818,557)	(129,769)	294	954,265
Comprehensive income:
Net income (loss)	1,299,797					1,232,432				67,365
Other comprehensive income (loss)	31,335
Other comprehensive income (loss)	31,052							17,612		13,440
Total comprehensive income	1,330,849
Increase in noncontrolling interests				3,583
Decrease in noncontrolling interests	(65,304)									(68,887)
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	14,869		162	25,445	(10,456)				(282)
Net proceeds from issuance of common stock	1,044,591		13,666	1,030,925
Conversion of preferred stock		(718,498)	12,712	705,786
Dividends paid:
Common stock dividends	(1,404,977)						(1,404,977)
Balances at end of period at Dec. 31, 2019	$ 16,506,627	$ 0	$ 411,005	$ 20,190,107	$ (78,955)	$ 7,353,966	$ (12,223,534)	$ (112,157)	$ 12	$ 966,183