Consolidated Statements of Changes in Equity - 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
Balance at Dec. 31, 2012									$ (824,008)	$ (66,182)	$ 102	$ 4,078	$ 5,651,170	$ 4,765,160	$ 167,320	$ 4,932,480
Balance (in Shares) at Dec. 31, 2012											102,000	407,782,000
Contributions from noncontrolling interests															1,026	1,026
Comprehensive income:
Net income									236,281					236,281	5,072	241,353
Other comprehensive income, net of tax:
Change in unrealized gain on marketable securities										6,773				6,773		6,773
Change in foreign currency translation adjustment										(5,573)				(5,573)	1,365	(4,208)
Redeemable noncontrolling interests income															(6,892)	(6,892)
Class J Depositary Share, and $1.40625 per
Dividends									(408,331)					(408,331)		(408,331)
Distributions to noncontrolling interests															(10,686)	(10,686)
Issuance of stock												$ 5	9,208	9,213		9,213
Issuance of stock (in Shares)												560,000
Surrender of common stock												$ (2)	(3,889)	(3,891)		(3,891)
Surrender of common stock (in Shares)												(247,000)
Exercise of common stock options												$ 16	30,193	30,209		$ 30,209
Exercise of common stock options (in Shares)												1,636,000				1,636,300
Acquisition of noncontrolling interests													(8,894)	(8,894)	(20,096)	$ (28,990)
Amortization of equity awards													11,470	11,470		11,470
Balance at Dec. 31, 2013									(996,058)	(64,982)	$ 102	$ 4,097	5,689,258	4,632,417	137,109	4,769,526
Balance (in Shares) at Dec. 31, 2013											102,000	409,731,000
Contributions from noncontrolling interests															6,259	6,259
Comprehensive income:
Net income									424,001					424,001	11,879	435,880
Other comprehensive income, net of tax:
Change in unrealized gain on marketable securities										20,202				20,202		20,202
Change in unrealized gain on interest rate swaps										(1,404)				(1,404)		(1,404)
Change in foreign currency translation adjustment										91,306				91,306	5,589	96,895
Redeemable noncontrolling interests income															(6,335)	(6,335)
Class J Depositary Share, and $1.40625 per
Dividends									(434,521)					(434,521)		(434,521)
Distributions to noncontrolling interests															(26,755)	(26,755)
Issuance of stock	$ 169,200	[1]	$ 387,200	[2]	$ 217,800	[3]	$ 169,100	[3]				$ 8	14,039	14,047		14,047
Issuance of stock (in Shares)	7,000,000	[1]	16,000,000	[2]	9,000,000	[3]	7,000,000	[3]				805,000
Surrender of common stock												$ (2)	(4,049)	(4,051)		(4,051)
Surrender of common stock (in Shares)												(190,000)
Exercise of common stock options												$ 15	23,859	23,874		$ 23,874
Exercise of common stock options (in Shares)												1,474,000				1,474,432
Acquisition of noncontrolling interests													(294)	(294)	(766)	$ (1,060)
Amortization of equity awards													9,208	9,208		9,208
Balance at Dec. 31, 2014									(1,006,578)	45,122	$ 102	$ 4,118	5,732,021	4,774,785	126,980	4,901,765
Balance (in Shares) at Dec. 31, 2014	70,000		16,000		9,000		7,000				102,000	411,820,000
Contributions from noncontrolling interests															66,163	66,163
Comprehensive income:
Net income									894,115					894,115	6,028	900,143
Other comprehensive income, net of tax:
Change in unrealized gain on marketable securities										(45,799)				(45,799)		(45,799)
Change in unrealized gain on interest rate swaps										(22)				(22)		(22)
Change in foreign currency translation adjustment										6,287				6,287		6,287
Redeemable noncontrolling interests income															(7,061)	(7,061)
Class J Depositary Share, and $1.40625 per
Dividends									(459,872)					(459,872)		(459,872)
Distributions to noncontrolling interests															(8,539)	(8,539)
Issuance of stock			$ 387,200	[2]	$ 217,800	[3]	$ 169,100	[3]				$ 8	485	493		493
Issuance of stock (in Shares)			16,000,000	[2]	9,000,000	[3]	7,000,000	[3]				824,000
Surrender of common stock												$ (2)	(5,680)	(5,682)		(5,682)
Surrender of common stock (in Shares)												(232,000)
Exercise of common stock options												$ 10	18,698	18,708		$ 18,708
Exercise of common stock options (in Shares)												1,019,000				1,019,240
Sale of interests in investments, net of tax of $16.0 million													23,993	23,993		$ 23,993
Acquisition of noncontrolling interests													262	262	(47,920)	(47,658)
Amortization of equity awards													14,032	14,032		14,032
Redemption of preferred stock											$ (70)		(174,930)	(175,000)		(175,000)
Redemption of preferred stock (in Shares)	(7,000,000)										(70,000)
Balance at Dec. 31, 2015									$ (572,335)	$ 5,588	$ 32	$ 4,134	$ 5,608,881	$ 5,046,300	$ 135,651	$ 5,181,951
Balance (in Shares) at Dec. 31, 2015			16,000		9,000		7,000				32,000	413,431,000

[1] The net proceeds received from this offering were used for general corporate purposes, including the reduction of borrowings outstanding under the Company's revolving credit facility and the redemption of shares of the Company's preferred stock.

[2] The net proceeds received from this offering were used for the redemption of all the outstanding depositary shares representing the Company's Class F preferred stock, which redemption occurred on August 15, 2012 with the remaining proceeds used towards the redemption of outstanding depositary shares representing the Company's Class G preferred stock, which redemption occurred on October 10, 2012 and general corporate purposes.

[3] The net proceeds received from this offering were used for general corporate purposes, including funding towards the repayment of maturing Senior Unsecured Notes.