Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Class A Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Stockholders' Equity [Member]	Non-Controlling Interests [Member]
Balance at Dec. 31, 2014	$ 1,500,886	$ 583	$ 2,027,404	$ (15,024)	$ (547,592)	$ 1,465,371	$ 35,515
Shares of class A common stock issued, net	1,029,535	349	1,029,186			1,029,535
Restricted class A common stock earned	9,599		9,599			9,599
Dividends reinvested	13		192		(179)	13
Deferred directors' compensation	281		281			281
Other comprehensive loss	(12,564)			(12,564)		(12,564)
Net income	146,288				131,564	131,564	14,724
Dividends declared on common stock	(136,674)				(136,674)	(136,674)
Distributions to non-controlling interests	(37,202)						(37,202)
Balance at Sep. 30, 2015	2,500,162	932	3,066,662	(27,588)	(552,881)	2,487,125	13,037
Balance at Dec. 31, 2015	2,505,731	937	3,070,200	(32,758)	(545,791)	2,492,588	13,143
Shares of class A common stock issued, net	2	2				2
Restricted class A common stock earned	14,190		14,190			14,190
Dividends reinvested	20		276		(256)	20
Deferred directors' compensation	282		282			282
Other comprehensive loss	(13,631)			(13,631)		(13,631)
Net income	193,040				184,921	184,921	8,119
Dividends declared on common stock	(174,678)				(174,678)	(174,678)
Distributions to non-controlling interests	(20,158)						(20,158)
Balance at Sep. 30, 2016	$ 2,504,798	$ 939	$ 3,084,948	$ (46,389)	$ (535,804)	$ 2,503,694	$ 1,104