Condensed Consolidated Statements of Changes in Equity (Unaudited) - USD ($) shares in Thousands, $ 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, 2015	$ (572,335)	$ 5,588	$ 32	$ 4,134	$ 5,608,881	$ 5,046,300	$ 135,651	$ 5,181,951
Balance at the beginning of the year (in shares) at Dec. 31, 2015			32	413,431
Contributions/deemed contributions from noncontrolling interests							507	507
Comprehensive income:
Net income	300,577					300,577	4,875	305,452
Other comprehensive income, net of tax:
Change in unrealized loss/gain on marketable securities		18				18		18
Change in unrealized loss on interest rate swaps		(432)				(432)		(432)
Change in foreign currency translation adjustment, net		971				971		971
Redeemable noncontrolling interests income							(3,240)	(3,240)
Dividends	(357,068)					(357,068)		(357,068)
Distributions to noncontrolling interests							(7,288)	(7,288)
Depositary Shares Issued (in shares)				10,701
Issuance of common stock, net				$ 107	285,757	285,864		285,864
Surrender of restricted stock (in shares)				(270)
Surrender of restricted stock				$ (3)	(6,901)	(6,904)		(6,904)
Exercise of common stock options (in shares)				1,151
Exercise of common stock options				$ 12	20,732	20,744		20,744
Amortization of equity awards					11,387	11,387		11,387
Balance at the beginning 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 at the beginning of the year (in shares) at Dec. 31, 2015			32	413,431
Other comprehensive income, net of tax:
Contributions/deemed contributions from noncontrolling interests							507	507
Balance at the end of the year at Sep. 30, 2016	(628,826)	6,145	$ 32	$ 4,250	5,919,856	5,301,457	130,505	5,431,962
Balance at the end of the year (in shares) at Sep. 30, 2016			32	425,013
Balance at the beginning 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 at the beginning of the year (in shares) at Dec. 31, 2016			32	425,034
Contributions/deemed contributions from noncontrolling interests							48,867	48,867
Comprehensive income:
Net income	341,179					341,179	13,926	355,105
Other comprehensive income, net of tax:
Change in unrealized loss/gain on marketable securities		(1,466)				(1,466)		(1,466)
Change in unrealized loss on interest rate swaps		308				308		308
Change in foreign currency translation adjustment, net		(6,335)				(6,335)		(6,335)
Redeemable noncontrolling interests income							(1,203)	(1,203)
Dividends	(379,933)					(379,933)		(379,933)
Distributions to noncontrolling interests							(13,513)	(13,513)
Depositary Shares Issued (in shares)				776
Issuance of common stock, net				$ 8	(8)
Surrender of restricted stock (in shares)				(239)
Surrender of restricted stock				$ (2)	(5,597)	(5,599)		(5,599)
Exercise of common stock options (in shares)				62
Exercise of common stock options					1,174	1,174		1,174
Amortization of equity awards					15,290	15,290		15,290
Balance at the beginning 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 at the beginning of the year (in shares) at Dec. 31, 2016			32	425,034
Other comprehensive income, net of tax:
Contributions/deemed contributions from noncontrolling interests							48,867	48,867
Issuance of preferred stock (in shares)			9
Issuance of preferred stock			$ 9		217,566	217,575		217,575
Depositary Shares Redeemed (in shares)			(9)
Redemption of preferred stock			$ (9)		(224,991)	(225,000)		(225,000)
Balance at the end of the year at Sep. 30, 2017	$ (715,621)	$ (1,727)	$ 32	$ 4,256	$ 5,926,392	$ 5,213,332	$ 194,812	$ 5,408,144
Balance at the end of the year (in shares) at Sep. 30, 2017			32	425,633