Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Additional Paid In Capital	Accumulated Other Comprehensive Loss	Accumulated Earnings	Non-controlling Interest in LLC	Class A Common Stock	Class A Common Stock Common Stock	Class B Common Stock	Class B Common Stock Common Stock
Beginning balance (in shares) at Jun. 30, 2018							20,555,000		17
Beginning balance at Jun. 30, 2018	$ 139,871	$ 108,360	$ (1,984)	$ 27,789	$ 5,502		$ 204		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	12,015			11,298	717
Stock based compensation, net of withholding taxes on vested equity awards (in shares)							(4,000)
Stock based compensation, net of withholding taxes on vested equity awards	(50)	(50)
Issuances of equity for services	71	71
Issuances of equity for exercise of options (in shares)							26,000
Issuances of equity for exercise of options	672	672
Increase in payable pursuant to the tax receivable agreement	(2,553)	(2,553)
Increase in deferred tax asset from step-up in tax basis	3,138	3,138
Exchange of LLC for Class A Common Stock (in shares)							199,000
Exchange of LLC for Class A Common Stock	2	1,047			(1,047)		$ 2
Cancellation of Class B Common Stock (in shares)									(1)
Cancellation of Class B Common Stock	0
Distributions to LLC Unit holders	(354)				(354)
Foreign currency translation adjustment	(419)		(404)	0	(15)
Ending balance (in shares) at Sep. 30, 2018							20,776,000		16
Ending balance at Sep. 30, 2018	152,393	110,685	(2,388)	39,087	4,803		$ 206		$ 0
Beginning balance (in shares) at Jun. 30, 2018							20,555,000		17
Beginning balance at Jun. 30, 2018	139,871	108,360	(1,984)	27,789	5,502		$ 204		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	27,013
Ending balance (in shares) at Dec. 31, 2018							20,836,000		16
Ending balance at Dec. 31, 2018	167,305	111,347	(2,755)	53,346	5,160		$ 207		$ 0
Beginning balance (in shares) at Sep. 30, 2018							20,776,000		16
Beginning balance at Sep. 30, 2018	152,393	110,685	(2,388)	39,087	4,803		$ 206		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	14,998			14,257	741
Stock based compensation, net of withholding taxes on vested equity awards (in shares)							57,000
Stock based compensation, net of withholding taxes on vested equity awards	(11)	(12)					$ 1
Issuances of equity for services	597	597
Issuances of equity for exercise of options (in shares)							3,000
Issuances of equity for exercise of options	77	77
Distributions to LLC Unit holders	(362)			2	(364)
Foreign currency translation adjustment	(387)		(367)		(20)
Ending balance (in shares) at Dec. 31, 2018							20,836,000		16
Ending balance at Dec. 31, 2018	167,305	111,347	(2,755)	53,346	5,160		$ 207		$ 0
Beginning balance (in shares) at Jun. 30, 2019						20,852,640	20,853,000	15	15
Beginning balance at Jun. 30, 2019	210,353	113,004	(2,828)	93,852	6,118		$ 207		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	16,682			15,859	823
Stock based compensation, net of withholding taxes on vested equity awards (in shares)							(5,000)
Stock based compensation, net of withholding taxes on vested equity awards	435	435
Issuances of equity for services	80	80
Repurchase and retirement of common stock (in shares)							(383,000)
Repurchase and retirement of common stock	(11,123)	(11,119)					$ (4)
Distributions to LLC Unit holders	(399)				(399)
Foreign currency translation adjustment	(648)		(623)		(25)
Ending balance (in shares) at Sep. 30, 2019							20,465,000		15
Ending balance at Sep. 30, 2019	213,677	102,400	(3,451)	108,008	6,517		$ 203		$ 0
Beginning balance (in shares) at Jun. 30, 2019						20,852,640	20,853,000	15	15
Beginning balance at Jun. 30, 2019	210,353	113,004	(2,828)	93,852	6,118		$ 207		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 34,280
Issuances of equity for exercise of options (in shares)	0
Ending balance (in shares) at Dec. 31, 2019						20,583,449	20,583,000	15	15
Ending balance at Dec. 31, 2019	$ 232,361	103,291	(2,836)	124,730	6,972		$ 204		$ 0
Beginning balance (in shares) at Sep. 30, 2019							20,465,000		15
Beginning balance at Sep. 30, 2019	213,677	102,400	(3,451)	108,008	6,517		$ 203		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,598			16,722	876
Stock based compensation, net of withholding taxes on vested equity awards (in shares)							116,000
Stock based compensation, net of withholding taxes on vested equity awards	237	236					$ 1
Issuances of equity for services (in shares)							2,000
Issuances of equity for services	655	655
Distributions to LLC Unit holders	(446)				(446)
Foreign currency translation adjustment	640		615		25
Ending balance (in shares) at Dec. 31, 2019						20,583,449	20,583,000	15	15
Ending balance at Dec. 31, 2019	$ 232,361	$ 103,291	$ (2,836)	$ 124,730	$ 6,972		$ 204		$ 0