Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Additional Paid-in Capital	Treasury Stock	(Accumulated Deficit) Retained Earnings	Noncontrolling Interests	Class A Common Stock	Class A Common Stock Common Stock	Class B Common Stock Common Stock
Beginning balance at Dec. 31, 2015	$ 68,054	$ 44,591	$ (1,542)	$ (3,093)	$ 28,083		$ 8	$ 7
Beginning balance (in shares) at Dec. 31, 2015			(150,993)				7,759,092	6,841,667
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	13,109			4,513	8,596
Issuance of Class A common stock under equity compensation plans	19	19
Issuance of Class A common stock under equity compensation plans (in shares)							246,164
Class A common stock withheld in Treasury from restricted share vesting	$ (160)		$ (160)
Class A common stock withheld in Treasury from restricted share vesting (in shares)	(21,397)		21,397				(21,397)
Forfeiture of restricted stock held in Treasury	$ 0	345	$ (345)
Forfeiture of restricted stock held in Treasury (in shares)			43,600				(43,600)
Issuances of restricted shares from Treasury	0	(721)	$ 721
Issuances of restricted shares from Treasury (in shares)			(75,749)				75,749
Issuances of Class A common stock from Treasury	21	(183)	$ 204
Issuances of Class A common stock from Treasury (in shares)			(20,697)				20,697
Stock compensation expense	3,792	3,792
Contributions (distributions)	(4,757)	6			(4,763)
Repurchases of Class A common stock (in shares)						0
Ending balance at Dec. 31, 2016	80,078	47,849	$ (1,122)	1,420	31,916		$ 8	$ 7
Ending balance (in shares) at Dec. 31, 2016			119,544				8,036,705	6,841,667
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	26,491			17,885	8,606
Issuance of Class A common stock under equity compensation plans	33	31					$ 2
Issuance of Class A common stock under equity compensation plans (in shares)							1,575,509
Class A common stock withheld in Treasury from restricted share vesting	$ (842)		$ (842)
Class A common stock withheld in Treasury from restricted share vesting (in shares)	(39,049)		39,049				(39,049)
Stock compensation expense	$ 7,404	7,404
Contributions (distributions)	(3,353)	2			(3,355)
Issuance of Class A common stock in private offering	16,487	16,484					$ 3
Issuance of Class A common stock in private offering (in shares)							3,000,000
Exchange of Series B Membership interest and exchange and cancellation of Class B common stock	(14,374)				(14,371)			$ (3)
Exchange of Series B Membership interest and exchange and cancellation of Class B common stock (in shares)								(3,000,000)
Repurchases of Class A common stock	(4,923)		$ (4,923)
Repurchases of Class A common stock (in shares)			222,184			(222,184)	(222,184)
Ending balance at Dec. 31, 2017	$ 107,001	$ 71,770	$ (6,887)	$ 19,305	$ 22,796		$ 13	$ 4
Ending balance (in shares) at Dec. 31, 2017			(380,777)				12,350,981	3,841,667