Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	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 the beginning of the year 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
Noncontrolling Interest, Increase from Subsidiary Equity Issuance							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 loss 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)
Dividends	(434,521)					(434,521)		(434,521)
Distributions to noncontrolling interests							(26,755)	(26,755)
Issuance of common stock (in shares)				805,000
Issuance of common stock				$ 8	14,039	14,047		14,047
Surrender of restricted stock (in shares)				(190,000)
Surrender of common stock				$ (2)	(4,049)	(4,051)		$ (4,051)
Exercise of common stock options (in shares)				1,474,000				1,474,432
Exercise of common stock options				$ 15	23,859	23,874		$ 23,874
Acquisition of noncontrolling interests					(294)	(294)	(766)	(1,060)
Amortization of equity awards					9,208	9,208		9,208
Balance at the end of the year 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			102,000	411,820,000
Other comprehensive income, net of tax:
Noncontrolling Interest, Increase from Subsidiary Equity Issuance							6,259	6,259
Noncontrolling Interest, Increase from Subsidiary Equity Issuance							66,163	66,163
Net income	894,115					894,115	6,028	900,143
Change in unrealized gain on marketable securities		(45,799)				(45,799)		(45,799)
Change in unrealized loss 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)
Dividends	(459,872)					(459,872)		(459,872)
Distributions to noncontrolling interests							(8,539)	(8,539)
Issuance of common stock (in shares)				824,000
Issuance of common stock				$ 8	485	493		493
Surrender of restricted stock (in shares)				(232,000)
Surrender of common stock				$ (2)	(5,680)	(5,682)		$ (5,682)
Exercise of common stock options (in shares)				1,019,000				1,019,240
Exercise of common stock options				$ 10	18,698	18,708		$ 18,708
Acquisition of noncontrolling interests					262	262	(47,920)	(47,658)
Amortization of equity awards					14,032	14,032		14,032
Balance at the end of the year 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			32,000	413,431,000
Other comprehensive income, net of tax:
Noncontrolling Interest, Increase from Subsidiary Equity Issuance							66,163	66,163
Sale of interests in investments, net of tax of $16.0 million					23,993	23,993		23,993
Redemption of preferred stock			$ (70)		(174,930)	(175,000)		(175,000)
Redemption of preferred stock (in shares)			(70,000)
Noncontrolling Interest, Increase from Subsidiary Equity Issuance							16,667	16,667
Net income	378,850					378,850	7,288	386,138
Change in unrealized gain on marketable securities		8				8		8
Change in unrealized loss on interest rate swaps		451				451		451
Change in foreign currency translation adjustment		(281)				(281)		(281)
Redeemable noncontrolling interests income							(4,349)	(4,349)
Dividends	(483,382)					(483,382)		(483,382)
Distributions to noncontrolling interests							(8,522)	(8,522)
Issuance of common stock (in shares)				10,711,000
Issuance of common stock				$ 107	286,314	286,421		286,421
Surrender of restricted stock (in shares)				(276,000)
Surrender of common stock				$ (3)	(7,005)	(7,008)		$ (7,008)
Exercise of common stock options (in shares)				1,168,000				1,167,819
Exercise of common stock options				$ 12	21,048	21,060		$ 21,060
Amortization of equity awards					13,720	13,720		13,720
Balance at the end of the year at Dec. 31, 2016	(676,867)	5,766	$ 32	$ 4,250	5,922,958	5,256,139	146,735	5,402,874
Balance (in shares) at Dec. 31, 2016			32,000	425,034,000
Other comprehensive income, net of tax:
Noncontrolling Interest, Increase from Subsidiary Equity Issuance							$ 16,667	$ 16,667