Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment	Additional Paid In Capital	Accumulated Other Comprehensive Loss	Accumulated Earnings	Accumulated Earnings Cumulative Effect, Period of Adoption, Adjustment	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, 2019									20,853,000		15
Beginning balance at Jun. 30, 2019	$ 210,353	$ (1,703)	$ 113,004	$ (2,828)	$ 93,852	$ (1,703)	$ 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									20,853,000		15
Beginning balance at Jun. 30, 2019	210,353	$ (1,703)	113,004	(2,828)	93,852	$ (1,703)	6,118		$ 207		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	58,146
Ending balance (in shares) at Mar. 31, 2020									20,537,000		15
Ending balance at Mar. 31, 2020	252,293		102,284	(4,914)	147,508		7,211		$ 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
Issuance 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									20,583,000		15
Ending balance at Dec. 31, 2019	232,361		103,291	(2,836)	124,730		6,972		$ 204		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	23,866				22,778		1,088
Stock based compensation, net of withholding taxes on vested equity awards (in shares)									1,000
Stock based compensation, net of withholding taxes on vested equity awards	789		789
Issuances of equity for services	58		58
Repurchase and retirement of common stock (in shares)									(100,000)
Repurchase and retirement of common stock	(2,710)		(2,709)						$ (1)
Issuances of equity for exercise of stock options (in shares)									12,000
Issuances of equity for exercise of stock options	377		377
Increase in payable pursuant to the tax receivable agreement	(440)		(440)
Increase in deferred tax asset from step-up in tax basis	574		574
Exchange of LLC Units for Class A Common Stock (in shares)									41,000
Exchange of LLC Units for Class A Common Stock	1		344				(344)		$ 1
Distributions to LLC Unit holders	(421)						(421)
Foreign currency translation adjustment	(2,162)			(2,078)			(84)
Ending balance (in shares) at Mar. 31, 2020									20,537,000		15
Ending balance at Mar. 31, 2020	252,293		102,284	(4,914)	147,508		7,211		$ 204		$ 0
Beginning balance (in shares) at Jun. 30, 2020								20,595,969	20,596,000	15	15
Beginning balance at Jun. 30, 2020	261,527		103,797	(3,132)	153,711		6,947		$ 204		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,038				21,093		945
Stock based compensation, net of withholding taxes on vested equity awards (in shares)									(3,000)
Stock based compensation, net of withholding taxes on vested equity awards	658		658
Issuances of equity for services	59		59
Issuances of equity for exercise of stock options (in shares)									9,000
Issuances of equity for exercise of stock options	300		300
Increase in payable pursuant to the tax receivable agreement	(330)		(330)
Increase in deferred tax asset from step-up in tax basis	480		480
Exchange of LLC Units for Class A Common Stock (in shares)									28,000		(2)
Exchange of LLC Units for Class A Common Stock	0		264				(264)
Distributions to LLC Unit holders	(449)						(449)
Foreign currency translation adjustment	652			630			22
Ending balance (in shares) at Sep. 30, 2020									20,630,000		13
Ending balance at Sep. 30, 2020	284,935		105,228	(2,502)	174,804		7,201		$ 204		$ 0
Beginning balance (in shares) at Jun. 30, 2020								20,595,969	20,596,000	15	15
Beginning balance at Jun. 30, 2020	261,527		103,797	(3,132)	153,711		6,947		$ 204		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 79,320
Issuances of equity for exercise of stock options (in shares)	11,625
Ending balance (in shares) at Mar. 31, 2021								20,844,019	20,844,000	11	11
Ending balance at Mar. 31, 2021	$ 345,605		109,692	(1,342)	229,825		7,223		$ 207		$ 0
Beginning balance (in shares) at Sep. 30, 2020									20,630,000		13
Beginning balance at Sep. 30, 2020	284,935		105,228	(2,502)	174,804		7,201		$ 204		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	22,147				21,225		922
Stock based compensation, net of withholding taxes on vested equity awards (in shares)									110,000
Stock based compensation, net of withholding taxes on vested equity awards	752		750						$ 2
Issuance of equity for services (in shares)									1,000
Issuances of equity for services	659		659
Increase in payable pursuant to the tax receivable agreement	(213)		(213)
Increase in deferred tax asset from step-up in tax basis	229		229
Exchange of LLC Units for Class A Common Stock (in shares)									12,000		(1)
Exchange of LLC Units for Class A Common Stock	0		118				(118)
Distributions to LLC Unit holders	(495)						(495)
Foreign currency translation adjustment	1,470			1,422			48
Ending balance (in shares) at Dec. 31, 2020									20,753,000		12
Ending balance at Dec. 31, 2020	309,484		106,771	(1,080)	196,029		7,558		$ 206		$ 0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	35,135				33,796		1,339
Stock based compensation, net of withholding taxes on vested equity awards (in shares)									2,000
Stock based compensation, net of withholding taxes on vested equity awards	1,400		1,400
Issuances of equity for services	59		59
Issuances of equity for exercise of stock options (in shares)									2,000
Issuances of equity for exercise of stock options	75		75
Increase in payable pursuant to the tax receivable agreement	(1,531)		(1,531)
Increase in deferred tax asset from step-up in tax basis	1,963		1,963
Exchange of LLC Units for Class A Common Stock (in shares)									87,000		(1)
Exchange of LLC Units for Class A Common Stock	1		955				(955)		$ 1
Distributions to LLC Unit holders	(710)						(710)
Foreign currency translation adjustment	(271)			(262)			(9)
Ending balance (in shares) at Mar. 31, 2021								20,844,019	20,844,000	11	11
Ending balance at Mar. 31, 2021	$ 345,605		$ 109,692	$ (1,342)	$ 229,825		$ 7,223		$ 207		$ 0