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, 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)	188,805,000					190,077,000				(1,272,000)
Other comprehensive income	1,496,000							1,496,000
Total comprehensive income	190,301,000
Net change in noncontrolling interests	12,238,000			(1,529,000)						13,767,000
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	98,980,000		1,784,000	102,238,000	(3,996,000)				(1,046,000)
Proceeds from issuance of common stock	3,447,408,000		64,400,000	3,383,008,000
Net proceeds from the issuance of preferred stock	277,687,000	287,500,000		(9,813,000)
Preferred stock redeemed, amount	(275,040,000)	(275,000,000)		6,202,000		(6,242,000)
Equity component of convertible debt	3,276,000		1,039,000	2,237,000
Option compensation expense	2,371,000								2,371,000
Cash dividends paid:
Common stock cash dividends	(460,936,000)						(460,936,000)
Preferred stock cash dividends	(52,527,000)						(52,527,000)
Balances at end of period at Sep. 30, 2012	10,522,405,000	1,022,917,000	259,522,000	10,502,057,000	(17,531,000)	2,077,641,000	(3,485,592,000)	(10,432,000)	7,445,000	166,378,000
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)	114,705,000					117,050,000				(2,345,000)
Other comprehensive income	(17,094,000)							(12,447,000)		(4,647,000)
Total comprehensive income	97,611,000
Net change in noncontrolling interests	159,749,000		1,109,000	23,410,000						135,230,000
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	174,760,000		2,756,000	176,840,000	(3,388,000)				(1,448,000)
Proceeds from issuance of common stock	1,630,281,000		23,000,000	1,607,281,000
Net proceeds from the issuance of preferred stock	0
Equity component of convertible debt	(555,000)		988,000	(1,543,000)
Option compensation expense	851,000								851,000
Cash dividends paid:
Common stock cash dividends	(618,992,000)						(618,992,000)
Preferred stock cash dividends	(49,805,000)						(49,805,000)
Balances at end of period at Sep. 30, 2013	$ 11,914,419,000	$ 1,022,917,000	$ 288,249,000	$ 12,349,678,000	$ (21,263,000)	$ 2,301,869,000	$ (4,363,376,000)	$ (23,475,000)	$ 5,864,000	$ 353,956,000