Consolidated Statements of Changes in Equity (USD $) In Thousands, except Share data, unless otherwise specified	Series F Preferred Stock [Member]		Series G Preferred Stock [Member]		Series H Preferred Stock [Member]	Series I Preferred Stock [Member]	Series J Preferred Stock [Member]	Series K Preferred Stock [Member]	Common Stock [Member] USD ($)	Common Stock [Member] Additional Paid-in Capital [Member] USD ($)	Common Stock [Member] Parent [Member] USD ($)	Common Stock [Member] USD ($)	Preferred Stock [Member] USD ($)	Preferred Stock [Member] Additional Paid-in Capital [Member] USD ($)	Preferred Stock [Member] Parent [Member] USD ($)	Preferred Stock [Member] USD ($)	Retained Earnings [Member] USD ($)	Accumulated Other Comprehensive Income (Loss) [Member] USD ($)	Preferred Stock [Member] USD ($)	Common Stock [Member] USD ($)	Additional Paid-in Capital [Member] USD ($)	Parent [Member] USD ($)	Noncontrolling Interest [Member] USD ($)	Total USD ($)
Balance at Dec. 31, 2011																	$ (702,999)	$ (107,660)	$ 954	$ 4,069	$ 5,492,022	$ 4,686,386	$ 193,757	$ 4,880,143
Balance (in Shares) at Dec. 31, 2011																			954,000	406,938,000
Contributions from noncontrolling interests																							1,384	1,384
Comprehensive income:
Net income																	266,073					266,073	14,202	280,275
Other comprehensive income, net of tax:
Change in unrealized gain on marketable securities																		3,013				3,013		3,013
Change in unrealized gain on interest rate swaps																		450				450		450
Change in foreign currency translation adjustment																		38,015				38,015	5,500	43,515
Redeemable noncontrolling interests																							(6,337)	(6,337)
Dividends																	(387,082)					(387,082)		(387,082)
Distributions to noncontrolling interests																							(15,328)	(15,328)
Issuance of stock									11	18,104	18,115	18,115	32	774,125	774,157	774,157
Issuance of stock (in Shares)	7,000,000	[1]	18,400,000	[2]					1,096,000				32,000
Surrender of common stock																				(1)	(2,072)	(2,073)		(2,073)
Surrender of common stock (in Shares)																				(111,000)
Repurchase of common stock																				(16)	(30,931)	(30,947)		(30,947)
Repurchase of common stock (in Shares)																				(1,636,000)				(106,010)
Exercise of common stock options																				15	22,576	22,591		22,591
Exercise of common stock options (in Shares)																				1,495,000				1,495,432
Acquisition of noncontrolling interests																					(95)	(95)	(25,858)	(25,953)
Amortization of equity awards																					11,557	11,557		11,557
Redemption of preferred stock																			(884)		(634,116)	(635,000)		(635,000)
Redemption of preferred stock (in Shares)																			(884,000)
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																							(6,892)	(6,892)
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)
Repurchase of common stock (in Shares)																								(144,727)
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																							(6,335)	(6,335)
Dividends																	(434,521)					(434,521)		(434,521)
Distributions to noncontrolling interests																							(26,755)	(26,755)
Issuance of stock																				8	14,039	14,047		14,047
Issuance of stock (in Shares)																				805,000
Surrender of common stock																				(2)	(4,049)	(4,051)		(4,051)
Surrender of common stock (in Shares)																				(190,000)
Repurchase of common stock (in Shares)																								(128,147)
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

[1] In connection with this redemption the Company recorded a non-cash charge of $6.2 million resulting from the difference between the redemption amount and the carrying amount of the Class F Preferred Stock on the Company's Consolidated Balance Sheets in accordance with the FASB's guidance on Distinguishing Liabilities from Equity. The $6.2 million was subtracted from net income to arrive at net income available to common shareholders and is used in the calculation of earnings per share for the year ended December 31, 2012.

[2] In connection with this redemption the Company recorded a non-cash charge of $15.5 million resulting from the difference between the redemption amount and the carrying amount of the Class G Preferred Stock on the Company's Consolidated Balance Sheets in accordance with the FASB's guidance on Distinguishing Liabilities from Equity. The $15.5 million was subtracted from net income to arrive at net income available to common shareholders and is used in the calculation of earnings per share for the year ended December 31, 2012.