Consolidated Statements of Equity (Unaudited) (USD $)	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, 2012	$ 10,520,519,000	$ 1,022,917,000	$ 260,396,000	$ 10,543,690,000	$ (17,875,000)	$ 2,184,819,000	$ (3,694,579,000)	$ (11,028,000)	$ 6,461,000	$ 225,718,000
Comprehensive income:
Net income (loss)	72,220,000					71,660,000				560,000
Other comprehensive income	(22,063,000)							(22,063,000)
Total comprehensive income	50,157,000
Net change in noncontrolling interests	(23,903,000)									(23,903,000)
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	52,228,000		853,000	55,600,000	(3,363,000)				(862,000)
Proceeds from issuance of common stock	294,000								294,000
Cash dividends paid:
Common stock cash dividends	(199,546,000)						(199,546,000)
Preferred stock cash dividends	(16,602,000)						(16,602,000)
Balances at end of period at Mar. 31, 2013	10,383,147,000	1,022,917,000	261,249,000	10,599,290,000	(21,238,000)	2,256,479,000	(3,910,727,000)	(33,091,000)	5,893,000	202,375,000
Balances at beginning of period at Dec. 31, 2013	11,756,331,000	1,017,361,000	289,461,000	12,418,520,000	(21,263,000)	2,329,869,000	(4,600,854,000)	(24,531,000)	6,020,000	341,748,000
Comprehensive income:
Net income (loss)	65,393,000					66,375,000				(982,000)
Other comprehensive income	(8,900,000)							(888,000)		(8,012,000)
Total comprehensive income	56,493,000
Net change in noncontrolling interests	(7,096,000)			(2,713,000)						(4,383,000)
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	63,919,000		1,397,000	67,725,000	(5,191,000)				(12,000)
Conversion of preferred stock	0	(11,111,000)	233,000	10,878,000
Option compensation expense	233,000								233,000
Cash dividends paid:
Common stock cash dividends	(230,801,000)						(230,801,000)
Preferred stock cash dividends	(16,353,000)						(16,353,000)
Balances at end of period at Mar. 31, 2014	$ 11,622,726,000	$ 1,006,250,000	$ 291,091,000	$ 12,494,410,000	$ (26,454,000)	$ 2,396,244,000	$ (4,848,008,000)	$ (25,419,000)	$ 6,241,000	$ 328,371,000