Consolidated Statement of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Accumulated Loss [Member]	Noncontrolling Interest [Member]	Parent Company [Member]	Parent Company [Member] Common Stock [Member]	Parent Company [Member] Treasury Stock [Member]	Parent Company [Member] Additional Paid-in Capital [Member]	Parent Company [Member] Accumulated Loss [Member]	Parent Company [Member] Accumulated Other Comprehensive Loss [Member]	Common Class A [Member] Parent Company [Member] Common Stock [Member]
Beginning balance at Dec. 31, 2016	$ 1,878,744		$ 891,246	$ 987,498	$ 875	$ (2,500)	$ 1,145,760	$ (94,270)	$ (62,367)
Beginning balance (in shares) at Dec. 31, 2016					87,521,651	110,964
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A common stock, net of issuance costs				22,509			22,500			$ 9
Issuance of Class A common stock, net of issuance costs (in shares)										931,561
Issuance of Class A common stock under equity incentive award plan					$ 2		(2)
Issuance of Class A common stock under equity incentive award plan, shares					231,311
Repurchase of shares for employee tax withholding	(97)			(97)		$ (97)
Repurchase of shares for employee tax withholding, shares						(4,182)
Stock-based compensation	4,085			4,085			4,085
Dividends declared	(110,168)			(110,168)			(110,168)
Acquisitions	390,389	$ 0
Distributions to noncontrolling interests	(13,701)	0	(13,701)
Other	(124)		(201)	77			77
Net loss	(60,521)		(50,566)	(9,955)				(9,955)
Other comprehensive income, net of tax	37,728		182	37,546					37,546
Ending balance at Sep. 30, 2017	2,148,844		1,217,349	931,495	$ 886	$ (2,597)	1,062,252	(104,225)	(24,821)
Ending balance (in shares) at Sep. 30, 2017					88,684,523	115,146
Beginning balance at Dec. 31, 2017	2,348,142		1,253,693	1,094,449	$ 980	$ (3,511)	1,234,846	(112,175)	(25,691)
Beginning balance (in shares) at Dec. 31, 2017					98,017,860	157,812
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A common stock under equity incentive award plan					$ 3		(3)
Issuance of Class A common stock under equity incentive award plan, shares					256,809
Repurchase of shares for employee tax withholding	(390)			(390)		$ (390)
Repurchase of shares for employee tax withholding, shares						(20,971)
Stock-based compensation	3,517			3,517			3,517
Dividends declared	(124,212)			(124,212)			(67,747)	(56,465)
Acquisitions	52,493	0	52,493
Sale of subsidiaries	(32,278)	4,632	(32,278)
Distributions to noncontrolling interests	(28,867)	$ 0	(28,867)
Other	(163)			(163)			(163)
Net loss	(45,941)		(201,986)	156,045				156,045
Other comprehensive income, net of tax	12,271		2,296	9,975					9,975
Ending balance at Sep. 30, 2018	$ 2,184,572		$ 1,045,351	$ 1,139,221	$ 983	$ (3,901)	$ 1,170,450	$ (12,595)	$ (15,716)
Ending balance (in shares) at Sep. 30, 2018					98,274,669	178,783