CONSOLIDATED STATEMENT OF EQUITY - USD ($) $ in Thousands	Total	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Class A Common Stock	Class A Common Stock Common Stock	Class B Common Stock	Class B Common Stock Common Stock
BALANCE (shares) at Dec. 31, 2016							64,558,207		25,670,684
BALANCE at Dec. 31, 2016	$ 557,936	$ 843,691	$ (255,804)	$ (807)	$ (30,047)		$ 646		$ 257
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net of issuance costs (shares)							12,000,000
Issuance of common stock, net of issuance costs	487,883	487,763					$ 120
Dividends declared and paid on Class A and Class B Common Stock	(34,744)		(34,744)
Class A Common Stock issued pursuant to employee benefit plans (shares)							435,619
Repurchases of Class A Common Stock	15,207	15,203					$ 4
Distributions to noncontrolling interests, net	(18,048)				(18,048)
Net income	116,738		101,847		14,891
BALANCE (shares) at Jun. 30, 2017							76,993,826		25,670,684
BALANCE at Jun. 30, 2017	1,124,972	1,346,657	(188,701)	(807)	(33,204)		$ 770		$ 257
BALANCE (shares) at Dec. 31, 2017						76,071,145	76,071,145	25,670,684	25,670,684
BALANCE at Dec. 31, 2017	1,534,366	1,320,298	248,845	(1,423)	(34,372)		$ 761		$ 257
Cumulative effect of adoption of new accounting standard at Dec. 31, 2017	2,100		2,100
Increase (Decrease) in Stockholders' Equity
Dividends declared and paid on Class A and Class B Common Stock	(36,794)		(36,794)
Class A Common Stock issued pursuant to employee benefit plans (shares)							505,835
Repurchases of Class A Common Stock	15,958	15,953					$ 5
Distributions to noncontrolling interests, net	(3,516)				(3,516)
Net income	73,304		71,165		2,139
BALANCE (shares) at Jun. 30, 2018						76,576,980	76,576,980	25,670,684	25,670,684
BALANCE at Jun. 30, 2018	$ 1,585,418	$ 1,336,251	$ 285,316	$ (1,423)	$ (35,749)		$ 766		$ 257