Consolidated Statements of Equity (Unaudited) - 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)	632,528					622,621				9,907
Other comprehensive income	50,486							28,291		22,195
Total comprehensive income	683,014
Increase in noncontrolling interests	17,342			9,784						7,558
Amounts related to stock incentive plans, net of forfeitures	7,935		337	17,151	(7,611)				(1,942)
Proceeds from issuance of common stock	530,467		7,513	522,954
Redemption of preferred stock	(287,509)	(287,500)		9,760		(9,769)
Redemption of equity membership units	5,545		91	5,465	(11)
Conversion of preferred stock	(247)	(247)
Option compensation expense	10								10
Cash dividends paid:
Common stock dividends	(955,631)						(955,631)
Preferred stock dividends	(37,734)						(37,734)
Balances at end of period at Sep. 30, 2017	15,244,664	718,503	371,012	17,564,805	(62,363)	5,416,427	(9,138,346)	(141,240)	1,127	514,739
Balances at beginning 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)	706,908					691,515				15,393
Other comprehensive income	(36,890)							(27,026)		(9,864)
Total comprehensive income	670,018
Increase in noncontrolling interests	419,543									453,682
Decrease in noncontrolling interests				(34,139)
Amounts related to stock incentive plans, net of forfeitures	18,924		172	23,127	(4,194)				(181)
Proceeds from issuance of common stock	241,572		3,732	237,840
Conversion of preferred stock	0	(5)		5
Cash dividends paid:
Common stock dividends	(971,280)						(971,280)
Preferred stock dividends	(35,028)						(35,028)
Balances at end of period at Sep. 30, 2018	$ 15,269,201	$ 718,498	$ 376,353	$ 17,889,514	$ (68,753)	$ 6,008,095	$ (10,478,020)	$ (138,491)	$ 489	$ 961,516