Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Class A Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive (Loss) Income [Member]	Accumulated Deficit [Member]	Stockholders' Equity [Member]	Non-Controlling Interests [Member]
Balance at Dec. 31, 2016	$ 2,493,603	$ 945	$ 3,089,997	$ (56,202)	$ (541,137)	$ 2,493,603
Shares of class A common stock issued, net	3	3				3
Restricted class A common stock earned	11,675		11,675			11,675
Issuance of convertible notes	856		856			856
Dividends reinvested	16		213		(197)	16
Deferred directors' compensation	188		188			188
Other comprehensive income	15,694			15,694		15,694
Net income	102,018				102,018	102,018
Dividends declared on common stock	(117,580)				(117,580)	(117,580)
Balance at Jun. 30, 2017	2,506,473	948	3,102,929	(40,508)	(556,896)	2,506,473
Balance at Dec. 31, 2017	2,917,406	1,079	3,506,861	(29,706)	(567,168)	2,911,066	$ 6,340
Shares of class A common stock issued, net	102,498	35	102,463			102,498
Restricted class A common stock earned	13,501		13,501			13,501
Issuance of convertible notes	1,462		1,462			1,462
Conversion of convertible notes	(20)		(20)			(20)
Dividends reinvested	27		250		(223)	27
Deferred directors' compensation	250		250			250
Other comprehensive income	(2,430)			(2,430)		(2,430)
Net income	133,624				133,271	133,271	353
Dividends declared on common stock	(136,145)				(136,145)	(136,145)
Contributions from non-controlling interests	2,475						2,475
Distributions to non-controlling interests	(3,986)						(3,986)
Balance at Jun. 30, 2018	$ 3,028,662	$ 1,114	$ 3,624,767	$ (32,136)	$ (570,265)	$ 3,023,480	$ 5,182