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, 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)	65,393,000					66,375,000				(982,000)
Other comprehensive income	(8,900,000)							(888,000)		(8,012,000)
Total comprehensive income	56,493,000
Net change in noncontrolling interests	(7,096,000)			(2,713,000)						(4,383,000)
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	63,919,000		1,397,000	67,725,000	(5,191,000)				(12,000)
Proceeds from issuance of common stock	0		0	0
Conversion of preferred stock		(11,111,000)	233,000	10,878,000
Equity component of convertible debt	0
Option compensation expense	233,000								233,000
Cash dividends paid:
Common stock cash dividends	(230,801,000)						(230,801,000)
Preferred stock cash dividends	(16,353,000)						(16,353,000)
Balances at end of period at Mar. 31, 2014	11,622,726,000	1,006,250,000	291,091,000	12,494,410,000	(26,454,000)	2,396,244,000	(4,848,008,000)	(25,419,000)	6,241,000	328,371,000
Balances at beginning 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)	5,507,000	297,896,000
Comprehensive income:
Net income (loss)	209,076,000					207,151,000				1,925,000
Other comprehensive income	(43,043,000)							(30,487,000)		(12,556,000)
Total comprehensive income	166,033,000
Net change in noncontrolling interests	70,757,000			(4,540,000)						75,297,000
Amounts related to issuance of common stock from dividend reinvestment and stock incentive plans, net of forfeitures	67,236,000		1,001,000	73,642,000	(6,132,000)				(1,275,000)
Proceeds from issuance of common stock	1,423,935,000		19,550,000	1,404,385,000
Conversion of preferred stock	0
Equity component of convertible debt	5,643,000		1,048,000	4,595,000
Option compensation expense	217,000								217,000
Cash dividends paid:
Common stock cash dividends	(272,569,000)						(272,569,000)
Preferred stock cash dividends	(16,352,000)						(16,352,000)
Balances at end of period at Mar. 31, 2015	$ 14,917,949,000	$ 1,006,250,000	$ 350,434,000	$ 16,218,794,000	$ (41,373,000)	$ 3,049,173,000	$ (5,924,844,000)	$ (107,496,000)	$ 4,449,000	$ 362,562,000