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)	542,198					536,896				5,302
Other comprehensive income	16,949							5,907		11,042
Total comprehensive income	559,147
Decrease in noncontrolling interests	(10,979)			(4,247)						(6,732)
Amounts related to stock incentive plans, net of forfeitures	2,661		337	11,803	(7,583)				(1,896)
Proceeds from issuance of common stock	423,532		6,026	417,506
Redemption of preferred stock	(287,509)	(287,500)		9,760		(9,769)
Redemption of equity membership units	5,544		91	5,464	(11)
Option compensation expense	10								10
Cash dividends paid:
Common stock dividends	(634,296)						(634,296)
Preferred stock dividends	(26,059)						(26,059)
Balances at end of period at Jun. 30, 2017	15,313,523	718,750	369,525	17,439,977	(62,335)	5,330,702	(8,805,336)	(163,624)	1,173	484,691
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)	623,001					615,455				7,546
Other comprehensive income	(33,797)							(21,166)		(12,631)
Total comprehensive income	589,204
Decrease in noncontrolling interests	(66,635)			(27,979)						(38,656)
Amounts related to stock incentive plans, net of forfeitures	12,941		168	16,886	(4,102)				(11)
Proceeds from issuance of common stock	9,975		184	9,791
Conversion of preferred stock	0	(5)		5
Cash dividends paid:
Common stock dividends	(647,098)						(647,098)
Preferred stock dividends	(23,352)						(23,352)
Balances at end of period at Jun. 30, 2018	$ 14,800,487	$ 718,498	$ 372,801	$ 17,661,384	$ (68,661)	$ 5,932,035	$ (10,142,162)	$ (132,631)	$ 659	$ 458,564