CONSOLIDATED STATEMENT OF EQUITY (DEFICIT) - 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	(16,257)		(16,257)
Class A Common Stock issued pursuant to employee benefit plans (shares)							376,262
Repurchases of Class A Common Stock	12,342	12,339					$ 3
Distributions to noncontrolling interests, net	(15,708)				(15,708)
Net income	70,703		57,202		13,501
BALANCE (shares) at Mar. 31, 2017							76,934,469		25,670,684
BALANCE at Mar. 31, 2017	1,096,899	1,343,793	(214,859)	(807)	(32,254)		$ 769		$ 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	(18,392)		(18,392)
Class A Common Stock issued pursuant to employee benefit plans (shares)							438,429
Repurchases of Class A Common Stock	12,138	12,134					$ 4
Distributions to noncontrolling interests, net	(2,663)				(2,663)
Net income	43,994		43,123		871
BALANCE (shares) at Mar. 31, 2018						76,509,574	76,509,574	25,670,684	25,670,684
BALANCE at Mar. 31, 2018	$ 1,571,543	$ 1,332,432	$ 275,676	$ (1,423)	$ (36,164)		$ 765		$ 257