Condensed Consolidated Statements of Changes in Equity (Unaudited) - 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
Dividends	$ (237,135)					$ (237,135)		$ (237,135)
Distributions to noncontrolling interests							(6,299)	(6,299)
Issuance of common stock (in shares)				5,839
Issuance of common stock				$ 59	139,068	139,127		139,127
Surrender of restricted stock (in shares)				(251)
Surrender of restricted stock				$ (3)	(6,439)	(6,442)		(6,442)
Exercise of common stock options (in shares)				979
Exercise of common stock options				$ 10	17,462	17,472		17,472
Amortization of equity awards					9,121	9,121		9,121
Balance at the end of the year at Jun. 30, 2016	(465,348)	7,150	$ 32	$ 4,200	5,768,093	5,314,127	130,558	5,444,685
Balance at the beginning of the year (in shares) at Dec. 31, 2015			32	413,431
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
Contributions/deemed contributions from noncontrolling interests							475	475
Comprehensive income:
Net income	344,122					344,122	2,878	347,000
Other comprehensive income, net of tax:
Change in unrealized loss/gain on marketable securities		(33)				(33)		(33)
Change in unrealized loss on interest rate swaps		(759)				(759)		(759)
Change in foreign currency translation adjustment		2,354				2,354		2,354
Redeemable noncontrolling interests income							(2,147)	(2,147)
Balance at the end of the year (in shares) at Jun. 30, 2016			32	419,998
Dividends	(252,953)					(252,953)		(252,953)
Distributions to noncontrolling interests							(12,691)	(12,691)
Issuance of common stock (in shares)				776
Issuance of common stock				$ 8	(8)
Surrender of restricted stock (in shares)				(224)
Surrender of restricted stock				$ (2)	(5,322)	(5,324)		(5,324)
Exercise of common stock options (in shares)				51
Exercise of common stock options					973	973		973
Amortization of equity awards					12,032	12,032		12,032
Balance at the end of the year at Jun. 30, 2017	(709,671)	6,073	$ 32	$ 4,256	5,930,633	5,231,323	194,279	5,425,602
Balance at the beginning of the year (in shares) at Dec. 31, 2016			32	425,034
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
Contributions/deemed contributions from noncontrolling interests							48,604	48,604
Comprehensive income:
Net income	$ 220,149					220,149	12,740	232,889
Other comprehensive income, net of tax:
Change in unrealized loss/gain on marketable securities		(1,619)				(1,619)		(1,619)
Change in unrealized loss on interest rate swaps		205				205		205
Change in foreign currency translation adjustment		$ 1,721				$ 1,721		1,721
Redeemable noncontrolling interests income							$ (1,109)	$ (1,109)
Balance at the end of the year (in shares) at Jun. 30, 2017			32	425,637