Consolidated Statements of Equity (USD $)	Total	Preferred Stock	Common Stock	Capital in Excess of Par Value	Treasury Stock	Cumulative Net Income	Cumulative Dividends	Accumulated Other Comprehensive Income	Other Equity	Noncontrolling Interests
Balances at beginning of period at Dec. 31, 2011	$ 7,278,647,000	$ 1,010,417,000	$ 192,299,000	$ 7,019,714,000	$ (13,535,000)	$ 1,893,806,000	$ (2,972,129,000)	$ (11,928,000)	$ 6,120,000	$ 153,883,000
Comprehensive income:
Net income (loss)	295,775,000					297,255,000				(1,480,000)
Other comprehensive income	900,000							900,000
Total comprehensive Income	296,675,000
Net changes in noncontrolling interests	66,179,000			(7,136,000)						73,315,000
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	145,739,000		2,658,000	149,955,000	(4,340,000)				(2,534,000)
Net proceeds from sale of common stock	3,446,932,000		64,400,000	3,382,532,000
Net proceeds from issuance of preferred stock	277,687,000	(275,000,000)		6,202,000
Equity component of convertible debt	3,275,000
Equity consideration in business combinations	0
Conversion of preferred stock	0
Option compensation expense	2,875,000								2,875,000
Cash dividends paid:
Common stock cash dividends	(653,321,000)						(653,321,000)
Preferred stock cash dividends	(69,129,000)						(69,129,000)
Balances at end 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)	139,563,000					145,050,000				(5,487,000)
Other comprehensive income	(20,000,000)							(13,503,000)
Total comprehensive Income	119,563,000
Net changes in noncontrolling interests	152,938,000			23,815,000						128,014,000
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	238,746,000		3,852,000	239,837,000	(3,388,000)				(1,555,000)
Net proceeds from sale of common stock	1,630,281,000		23,000,000	1,607,281,000
Net proceeds from issuance of preferred stock	0
Equity consideration in business combinations	(555,000)		988,000	(1,543,000)
Redemption of preferred stock	0
Option compensation expense	1,114,000								1,114,000
Cash dividends paid:
Common stock cash dividends	(839,939,000)						(839,939,000)
Preferred stock cash dividends	(66,336,000)						(66,336,000)
Balances at end 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)	511,811,000					512,153,000				(342,000)
Other comprehensive income	(67,303,000)							(52,478,000)		(14,825,000)
Total comprehensive Income	444,508,000
Net changes in noncontrolling interests	(46,338,000)			(17,653,000)						(28,685,000)
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	287,529,882.21		4,958,000	297,975,000	(13,978,000)				(1,425,117.79)
Net proceeds from sale of common stock	2,063,982,000		33,925,000	2,030,057,000
Net proceeds from issuance of preferred stock	0
Equity component of convertible debt	1,193,000		258,000	935,000
Redemption of preferred stock	0
Conversion of preferred stock		(11,111,000)	233,000	10,878,000
Option compensation expense	911,642.46								911,642.46
Cash dividends paid:
Common stock cash dividends	(969,661,000)						(969,661,000)
Preferred stock cash dividends	(65,408,000)						(65,408,000)
Balances at end of period at Dec. 31, 2014	$ 13,473,049,000	$ 1,006,250,000	$ 328,835,000	$ 14,740,712,000	$ (35,241,000)	$ 2,842,022,000	$ (5,635,923,000)	$ (77,009,000)	$ 5,506,524.67	$ 297,896,000