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, 2009	$ 3,807,451,000		$ 288,683,000	$ 123,385,000	$ 3,900,666,000	$ (7,619,000)	$ 1,547,669,000	$ (2,057,658,000)	$ (2,891,000)	$ 4,804,000	$ 10,412,000
Comprehensive income:
Net income (loss)	82,850,000						83,233,000				(383,000)
Other comprehensive income:
Unrealized gain (loss) on equity investments	(95,000)								(95,000)
Cash flow hedge activity	(8,473,000)								(8,473,000)
Total comprehensive income	74,282,000
Contributions by noncontrolling interests	123,520,000				41,423,000						82,097,000
Distributions to noncontrolling interests	(2,649,000)										(2,649,000)
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	68,252,000			1,691,000	70,540,000	(3,733,000)				(246,000)
Proceeds from issuance of common stock	422,937,000			9,631,000	413,306,000
Redemption of preferred stock	(165,000)		(165,000)
Conversion of preferred stock			(13,518,000)	339,000	13,179,000
Equity component of convertible debt	(9,689,000)				(9,689,000)
Option compensation expense	1,414,000									1,414,000
Cash dividends paid:
Common stock cash dividends	(255,217,000)							(255,217,000)
Preferred stock cash dividends	(16,340,000)							(16,340,000)
Balances at end of period at Sep. 30, 2010	4,213,796,000		275,000,000	135,046,000	4,429,425,000	(11,352,000)	1,630,902,000	(2,329,215,000)	(11,459,000)	5,972,000	89,477,000
Balances at beginning of period at Jun. 30, 2010
Other comprehensive income:
Unrealized gain (loss) on equity investments	42,000
Cash flow hedge activity	(2,975,000)
Option compensation expense										221,000
Balances at end of period at Sep. 30, 2010	4,213,796,000									5,972,000
Balances at beginning of period at Dec. 31, 2010	4,733,100,000	[1]	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)	170,791,000						173,094,000				(2,303,000)
Other comprehensive income:
Unrealized gain (loss) on equity investments	(314,000)								(314,000)
Cash flow hedge activity	1,059,000								1,059,000
Total comprehensive income	171,536,000
Contributions by noncontrolling interests	29,342,000				6,647,000						22,695,000
Distributions to noncontrolling interests	36,268,000										36,268,000
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	101,832,000			2,124,000	102,937,000	(2,183,000)				(1,046,000)
Proceeds from issuance of common stock	1,394,465,000			29,493,000	1,364,972,000
Proceeds from issuance of preferred stock	696,437,000		718,750,000		(22,313,000)
Option compensation expense	1,641,000									1,641,000
Cash dividends paid:
Common stock cash dividends	(355,651,000)							(355,651,000)
Preferred stock cash dividends	(43,268,000)							(43,268,000)
Balances at end of period at Sep. 30, 2011	6,693,166,000		1,010,417,000	178,772,000	6,384,711,000	(13,535,000)	1,849,290,000	(2,826,800,000)	(10,354,000)	6,292,000	114,373,000
Balances at beginning of period at Jun. 30, 2011
Other comprehensive income:
Unrealized gain (loss) on equity investments	(400,000)
Cash flow hedge activity	191,000
Option compensation expense										301,000
Balances at end of period at Sep. 30, 2011	$ 6,693,166,000									$ 6,292,000

[1] NOTE: The consolidated balance sheet at December 31, 2010 has been derived from the audited financial statements at that date but does not include all of the information and footnotes required by U.S. generally accepted accounting principles for complete financial statements.