Condensed Consolidated Statements of Changes in Equity (Unaudited) - USD ($) $ in Thousands	Series H Preferred Stock [Member]	Series I Preferred Stock [Member]	Series J Preferred Stock [Member]	Series K Preferred Stock [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Parent [Member]	Noncontrolling Interest [Member]	Total
Beginning balance at Dec. 31, 2013					$ (996,058)	$ (64,982)	$ 102	$ 4,097	$ 5,689,258	$ 4,632,417	$ 137,109	$ 4,769,526
Beginning balance (in Shares) at Dec. 31, 2013							102,000	409,731,000
Contributions from noncontrolling interests											3,098	3,098
Comprehensive income:
Net income					371,220					371,220	13,899	385,119
Change in unrealized gain on marketable securities						$ 13,980				13,980		13,980
Change in foreign currency translation adjustment						(17,618)				(17,618)	(189)	(17,807)
Redeemable noncontrolling interests											(4,779)	(4,779)
Class J Depositary Share. and $1.0547 per
Distributions to noncontrolling interests											(25,150)	(25,150)
Issuance of common stock								$ 8	13,827	13,835		13,835
Issuance of common stock (in Shares)								805,000
Surrender of restricted stock								$ (2)	(3,979)	(3,981)		(3,981)
Surrender of restricted stock (in Shares)								(187,000)
Exercise of common stock options								$ 10	16,077	16,087		16,087
Exercise of common stock options (in Shares)								989,000
Acquisition of noncontrolling interests									(53)	(53)	(766)	(819)
Amortization of equity awards									7,699	7,699		7,699
Ending balance at Sep. 30, 2014					(945,949)	(68,620)	$ 102	$ 4,113	5,722,829	4,712,475	123,222	4,835,697
Ending balance (in Shares) at Sep. 30, 2014							102,000	411,338,000
Class J Depositary Share. and $1.0547 per
Dividends					(321,111)					(321,111)		(321,111)
Beginning balance at Dec. 31, 2014					(1,006,578)	45,122	$ 102	$ 4,118	5,732,021	4,774,785	126,980	4,901,765
Beginning balance (in Shares) at Dec. 31, 2014							102,000	411,820,000
Contributions from noncontrolling interests											66,163	66,163
Comprehensive income:
Net income					514,914					514,914	6,518	521,432
Change in unrealized gain on marketable securities						(44,418)				(44,418)		(44,418)
Change in unrealized loss on interest rate swaps						(475)				(475)		(475)
Change in foreign currency translation adjustment						(14,973)				(14,973)		(14,973)
Redeemable noncontrolling interests											(5,822)	(5,822)
Class J Depositary Share. and $1.0547 per
Distributions to noncontrolling interests											(6,706)	(6,706)
Issuance of common stock								$ 8	480	488		488
Issuance of common stock (in Shares)								784,000
Surrender of restricted stock								$ (2)	(5,602)	(5,604)		(5,604)
Surrender of restricted stock (in Shares)								(227,000)
Exercise of common stock options								$ 8	15,559	15,567		15,567
Exercise of common stock options (in Shares)								846,000
Sale of interests in investments, net of tax of $16 million									23,993	23,993		23,993
Acquisition of noncontrolling interests									(6,437)	(6,437)	(25,189)	(31,626)
Amortization of equity awards									10,956	10,956		10,956
Ending balance at Sep. 30, 2015					(832,746)	$ (14,744)	$ 102	$ 4,132	$ 5,770,970	4,927,714	$ 161,944	5,089,658
Ending balance (in Shares) at Sep. 30, 2015	70,000	16,000	9,000	7,000			102,000	413,223,000
Class J Depositary Share. and $1.0547 per
Dividends					$ (341,082)					$ (341,082)		$ (341,082)