UNAUDITED CONSOLIDATED STATEMENT OF CHANGES IN EQUITY - USD ($) $ in Thousands	Total	Common Class A	Common Class B	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings	Non-Controlling Interests
Beginning Balance at Dec. 31, 2017	$ 99,289	$ 180		$ 7,915	$ (5)	$ 24,214	$ 66,985
Beginning Balance (in shares) at Dec. 31, 2017		18,096,554	50,709,673
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of Non-Cash Compensation	1,260			339			921
Amortization of Non-Cash Compensation (in shares)		10,000	26,178
Issuance of Shares under Equity Incentive Plan	4,191			1,096			3,095
Issuance of Shares under Equity Incentive Plan (in shares)			300,931
Sale of Shares under Equity Incentive Plan	4			1			3
Sale of Shares under Equity Incentive Plan (in shares)			547
Directors' Share Grants	245			64			181
Net Income	17,666					3,523	14,143
Foreign Currency Translation Adjustments	68				(18)		86
Repurchase and Retirement of Class A Common Stock	(3,203)	$ (3)		(3,200)
Repurchase and Retirement Shares/Units (in shares)		(293,130)	(3,870)
Repurchase and Retirement of Class B Units	(41)			(11)			(30)
Class A Cash Dividends Declared and Paid ($0.49 per share)	(7,560)					(7,560)
Distributions to Non-Controlling Interests	(29,719)						(29,719)
Other				(404)			404
Ending Balance at Mar. 31, 2018	82,200	$ 177		5,800	(23)	20,177	56,069
Ending Balance (in shares) at Mar. 31, 2018		17,813,424	51,033,459
Beginning Balance at Dec. 31, 2018	99,008	$ 183		3,913	35	28,871	66,006
Beginning Balance (in shares) at Dec. 31, 2018		18,398,211	51,253,526
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of Non-Cash Compensation	1,554			414			1,140
Amortization of Non-Cash Compensation (in shares)		10,000	241,996
Issuance of Shares under Equity Incentive Plan	4,087			1,065			3,022
Issuance of Shares under Equity Incentive Plan (in shares)			715,874
Sale of Shares under Equity Incentive Plan	65			17			48
Sale of Shares under Equity Incentive Plan (in shares)			10,399
Directors' Share Grants	301			78			223
Net Income	15,942					3,102	12,840
Foreign Currency Translation Adjustments	63				(17)		80
Repurchase and Retirement of Class A Common Stock	(4,712)	$ (5)		(4,369)		(338)
Repurchase and Retirement Shares/Units (in shares)		(533,369)	(95,739)
Repurchase and Retirement of Class B Units	(675)			(176)			(499)
Class A Cash Dividends Declared and Paid ($0.49 per share)	(8,951)					(8,951)
Tax Impact of Transactions with Non-Controlling Shareholders	(207)			(207)
Contributions from Non-Controlling Interests	23						23
Distributions to Non-Controlling Interests	(25,665)						(25,665)
Other				$ (735)			735
Ending Balance at Mar. 31, 2019	$ 80,833	$ 178			$ 18	$ 22,684	$ 57,953
Ending Balance (in shares) at Mar. 31, 2019		17,874,842	52,126,056