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, 2015	$ 15,175,885	$ 1,006,250	$ 354,811	$ 16,478,300	$ (44,372)	$ 3,725,772	$ (6,846,056)	$ (88,243)	$ 4,098	$ 585,325
Comprehensive income:
Net income (loss)	735,771					728,408				7,363
Other comprehensive income	(52,377)							(62,941)		10,564
Total comprehensive income	683,394
Decrease in noncontrolling interests	(174,624)			(45,765)						(128,859)
Amounts related to stock incentive plans, net of forfeitures	30,470		689	38,888	(7,822)				(1,285)
Proceeds from issuance of common stock	519,342		7,203	512,139
Option compensation expense	207								207
Cash dividends paid:
Common stock	(921,381)						(921,381)
Preferred Stock	(49,055)						(49,055)
Balances at end of period at Sep. 30, 2016	15,264,238	1,006,250	362,703	16,983,562	(52,194)	4,454,180	(7,816,492)	(151,184)	3,020	474,393
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	(955,631)						(955,631)
Preferred Stock	(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