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, 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	(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
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]
Sale of Shares under Equity Incentive Plan (in shares)			16,137
Net Income	49,153
Repurchase and Retirement Shares/Units (in shares)		(709,466)	(109,357)
Ending Balance at Sep. 30, 2019	95,650	$ 176		59	63	28,454	66,898
Ending Balance (in shares) at Sep. 30, 2019		17,758,620	52,146,946
Beginning Balance at Mar. 31, 2019	80,833	$ 178			18	22,684	57,953
Beginning Balance (in shares) at Mar. 31, 2019		17,874,842	52,126,056
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of Non-Cash Compensation	1,666			425			1,241
Sale of Shares under Equity Incentive Plan	1						1
Sale of Shares under Equity Incentive Plan (in shares)			237
Directors' Share Grants	103			26			77
Net Income	16,295					3,364	12,931
Foreign Currency Translation Adjustments	(73)				19		(92)
Repurchase and Retirement of Class A Common Stock	(536)					(536)
Tax Impact of Transactions with Non-Controlling Shareholders	(110)			(110)
Contributions from Non-Controlling Interests	5						5
Distributions to Non-Controlling Interests	(6,972)						(6,972)
Other				(52)			52
Ending Balance at Jun. 30, 2019	91,212	$ 178		289	37	25,512	65,196
Ending Balance (in shares) at Jun. 30, 2019		17,874,842	52,126,293
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of Non-Cash Compensation	1,666			425			1,241
Sale of Shares under Equity Incentive Plan	31			8			23
Sale of Shares under Equity Incentive Plan (in shares)			5,501
Directors' Share Grants	104			27			77
Net Income	16,916					3,478	13,438
Foreign Currency Translation Adjustments	(104)				26		(130)
Options Exercised (in shares)		59,875	28,770
Repurchase and Retirement of Class A Common Stock	(1,486)	$ (2)		(377)			(1,107)
Repurchase and Retirement Shares/Units (in shares)		(176,097)	(13,618)
Repurchase and Retirement of Class B Units	(134)			(35)			(99)
Class A Cash Dividends Declared and Paid	(536)					(536)
Tax Impact of Transactions with Non-Controlling Shareholders	(120)			(120)
Contributions from Non-Controlling Interests	56						56
Distributions to Non-Controlling Interests	(11,955)						(11,955)
Other				(158)			158
Ending Balance at Sep. 30, 2019	95,650	$ 176		59	63	28,454	66,898
Ending Balance (in shares) at Sep. 30, 2019		17,758,620	52,146,946
Beginning Balance at Dec. 31, 2019	108,210	$ 179		4,829	(3)	26,439	76,766
Beginning Balance (in shares) at Dec. 31, 2019		18,009,350	52,879,323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of Non-Cash Compensation	2,052			479			1,573
Amortization of Non-Cash Compensation (in shares)		10,000	321,949
Issuance of Shares under Equity Incentive Plan	3,842			890			2,952
Issuance of Shares under Equity Incentive Plan (in shares)			637,349
Sale of Shares under Equity Incentive Plan	1,902			436			1,466
Sale of Shares under Equity Incentive Plan (in shares)			430,955
Directors' Share Grants	331			76			255
Net Income	769						769
Foreign Currency Translation Adjustments	(505)				122		(627)
Repurchase and Retirement of Class A Common Stock	(5,648)	$ (8)		(1,283)			(4,357)
Repurchase and Retirement Shares/Units (in shares)		(823,792)	(94,830)
Repurchase and Retirement of Class B Units	(565)			(131)			(434)
Class A Cash Dividends Declared and Paid	(8,172)					(8,172)
Tax Impact of Transactions with Non-Controlling Shareholders	(717)			(717)
Effect of Deconsolidation	(1,685)						(1,685)
Contributions from Non-Controlling Interests	641						641
Distributions to Non-Controlling Interests	(33,327)						(33,327)
Other				(1,224)			1,224
Ending Balance at Mar. 31, 2020	67,128	$ 171		3,355	119	18,267	45,216
Ending Balance (in shares) at Mar. 31, 2020		17,195,558	54,174,746
Beginning Balance at Dec. 31, 2019	108,210	$ 179		4,829	(3)	26,439	76,766
Beginning Balance (in shares) at Dec. 31, 2019		18,009,350	52,879,323
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of Shares under Equity Incentive Plan (in shares)			548,136
Net Income	29,192
Repurchase and Retirement Shares/Units (in shares)		(1,192,045)	(94,830)
Ending Balance at Sep. 30, 2020	84,959	$ 168		3,405	19	22,103	59,264
Ending Balance (in shares) at Sep. 30, 2020		16,844,111	54,275,121
Beginning Balance at Mar. 31, 2020	67,128	$ 171		3,355	119	18,267	45,216
Beginning Balance (in shares) at Mar. 31, 2020		17,195,558	54,174,746
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of Non-Cash Compensation	2,015			449			1,566
Sale of Shares under Equity Incentive Plan	291			65			226
Sale of Shares under Equity Incentive Plan (in shares)			96,600
Modification, shares		16,806	(16,806)
Directors' Share Grants	(106)			(23)			(83)
Net Income	12,849					2,198	10,651
Foreign Currency Translation Adjustments	283				(169)		452
Repurchase and Retirement of Class A Common Stock	(1,396)	$ (2)		(288)			(1,106)
Repurchase and Retirement Shares/Units (in shares)		(266,238)
Class A Cash Dividends Declared and Paid	(517)					(517)
Tax Impact of Transactions with Non-Controlling Shareholders	(92)			(92)
Contributions from Non-Controlling Interests	68						68
Distributions to Non-Controlling Interests	(1,899)						(1,899)
Other				34			(34)
Ending Balance at Jun. 30, 2020	78,624	$ 169		3,500	(50)	19,948	55,057
Ending Balance (in shares) at Jun. 30, 2020		16,946,126	54,254,540
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Amortization of Non-Cash Compensation	2,036			448			1,588
Sale of Shares under Equity Incentive Plan	74			16			58
Sale of Shares under Equity Incentive Plan (in shares)			20,581
Directors' Share Grants	14			3			11
Net Income	15,574					2,664	12,910
Foreign Currency Translation Adjustments	295				69		226
Repurchase and Retirement of Class A Common Stock	(516)	$ (1)		(113)			(402)
Repurchase and Retirement Shares/Units (in shares)		(102,015)
Class A Cash Dividends Declared and Paid	(509)					(509)
Tax Impact of Transactions with Non-Controlling Shareholders	(138)			(138)
Contributions from Non-Controlling Interests	51						51
Distributions to Non-Controlling Interests	(10,546)						(10,546)
Other				(311)			311
Ending Balance at Sep. 30, 2020	$ 84,959	$ 168		$ 3,405	$ 19	$ 22,103	$ 59,264
Ending Balance (in shares) at Sep. 30, 2020		16,844,111	54,275,121