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	5,810		5,810			5,810
Dividends reinvested	9		105		(96)	9
Deferred directors' compensation	94		94			94
Other comprehensive income (loss)	3,845			3,845		3,845
Net income	51,405				51,405	51,405
Dividends declared on common stock	(58,787)				(58,787)	(58,787)
Balance at Mar. 31, 2017	2,495,982	948	3,096,006	(52,357)	(548,615)	2,495,982
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	3	3				3
Restricted class A common stock earned	6,848		6,848			6,848
Issuance of convertible notes	1,462		1,462			1,462
Dividends reinvested	14		122		(108)	14
Deferred directors' compensation	125		125			125
Other comprehensive income (loss)	7,803			7,803		7,803
Net income	61,116				60,958	60,958	158
Dividends declared on common stock	(67,066)				(67,066)	(67,066)
Contributions from non-controlling interests	375						375
Distributions to non-controlling interests	(1,575)						(1,575)
Balance at Mar. 31, 2018	$ 2,926,511	$ 1,082	$ 3,515,418	$ (21,903)	$ (573,384)	$ 2,921,213	$ 5,298