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)	79,746,000					79,754,000				(8,000)
Other comprehensive income	(42,600,000)							(38,146,000)		(4,454,000)
Total comprehensive income	37,146,000
Net change in noncontrolling interests	198,739,000									198,739,000
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	109,564,000		1,689,000	112,601,000	(3,373,000)				(1,353,000)
Proceeds from issuance of common stock	1,630,636,000		23,000,000	1,607,636,000
Option compensation expense	570,000								570,000
Cash dividends paid:
Common stock cash dividends	(399,815,000)						(399,815,000)
Preferred stock cash dividends	(33,203,000)						(33,203,000)
Balances at end of period at Jun. 30, 2013	12,064,156,000	1,022,917,000	285,085,000	12,263,927,000	(21,248,000)	2,264,573,000	(4,127,597,000)	(49,174,000)	5,678,000	419,995,000
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)	153,205,000					154,556,000				(1,351,000)
Other comprehensive income	4,481,000						5,889,000			(1,408,000)
Total comprehensive income	157,686,000
Net change in noncontrolling interests	(11,548,000)			(4,680,000)						(6,868,000)
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	138,701,000		2,561,000	147,486,000	(11,026,000)				(320,000)
Proceeds from issuance of common stock	968,517,000		16,100,000	952,417,000
Conversion of preferred stock	0	(11,111,000)	233,000	10,878,000
Option compensation expense	459,000								459,000
Cash dividends paid:
Common stock cash dividends	(462,551,000)						(462,551,000)
Preferred stock cash dividends	(32,705,000)						(32,705,000)
Balances at end of period at Jun. 30, 2014	$ 12,514,890,000	$ 1,006,250,000	$ 308,355,000	$ 13,524,621,000	$ (32,289,000)	$ 2,484,425,000	$ (5,096,110,000)	$ (18,642,000)	$ 6,159,000	$ 332,121,000