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, 2010	$ 4,733,100,000	$ 291,667,000	$ 147,155,000	$ 4,932,468,000	$ (11,352,000)	$ 1,676,196,000	$ (2,427,881,000)	$ (11,099,000)	$ 5,697,000	$ 130,249,000
Comprehensive income:
Net income (loss)	214,019,000					217,610,000				(3,591,000)
Other comprehensive income	(829,000)							(829,000)
Total comprehensive Income	213,190,000
Net changes in noncontrolling interests	33,693,000			6,468,000						27,225,000
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	138,207,000		2,895,000	138,989,000	(2,183,000)				(1,494,000)
Net proceeds from sale of common stock	2,006,351,000		42,249,000	1,964,102,000
Net proceeds from issuance of preferred stock	696,437,000	718,750,000		(22,313,000)
Equity component of convertible debt	0
Equity consideration in business combinations	0
Conversion of preferred stock	0
Option compensation expense	1,917,000								1,917,000
Cash dividends paid:
Common stock cash dividends	(483,746,000)						(483,746,000)
Preferred stock cash dividends	(60,502,000)						(60,502,000)
Balances at end 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	287,500,000		(9,813,000)
Equity consideration in business combinations	3,275,000		1,039,000	2,236,000
Redemption of preferred stock	(275,040,000)	(275,000,000)		6,202,000		(6,242,000)
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)		(6,497,000)
Total comprehensive Income	119,563,000
Net changes in noncontrolling interests	152,938,000		1,109,000	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 component of convertible debt	(555,000)		988,000	(1,543,000)
Redemption of preferred stock	0
Conversion of preferred stock		(5,556,000)	116,000	5,440,000
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