Summary of Significant Accounting Policies - Impact on adoption of revenue recognition (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2016	Jun. 30, 2019	Jun. 30, 2018		Jun. 30, 2017		Jul. 01, 2018	Jun. 30, 2016
Summary of Significant Accounting Policies
Length of the school year that revenues were recognized over prior to adoption of ASC 606									10 months
Revenues	$ 256,314	$ 253,252	$ 254,872	$ 251,314	$ 238,874	$ 232,864	$ 217,211	$ 228,785	$ 1,015,752	$ 917,734		$ 888,519
Selling, administrative, and other operating expenses	75,207	59,382	60,183	102,578	69,939	62,267	61,958	96,282	297,350	290,446		305,617
Loss from operations	2,681	23,267	33,290	(13,752)	9,876	19,717	13,714	(17,762)	45,486	25,545		13,129
Net income					9,347	13,043	13,189	(8,159)	37,209	27,420		(459)
Net income attributable to common stockholders	3,317	$ 18,462	$ 23,712	$ (8,282)	9,347	$ 13,070	$ 13,259	$ (8,056)	37,209	27,620	[1]	451	[1]
Other current assets	12,307				10,388				12,307	10,388
Deposits and other assets	48,330				41,887				48,330	41,887
Total assets	819,606				741,963				819,606	741,963
Deferred revenue	22,828				23,114				22,828	23,114				$ 25,580
Total liabilities	186,241				154,774				186,241	154,774
Retained earnings (accumulated deficit)	22,447				(13,432)				22,447	(13,432)
Total stockholders’ equity	633,365				$ 587,189				633,365	$ 587,189		$ 574,346			$ 558,720
Adjustment due to ASC 606
Summary of Significant Accounting Policies
Revenues									(203)
Selling, administrative, and other operating expenses									(263)
Loss from operations									60
Net income									60
Net income attributable to common stockholders									60
Other current assets	(273)								(273)
Deposits and other assets	(629)								(629)
Total assets	(902)								(902)
Deferred revenue	(2,263)								(2,263)
Total liabilities	(2,263)								(2,263)
Retained earnings (accumulated deficit)	60								60
Total stockholders’ equity	60								60
Amounts under ASC 605
Summary of Significant Accounting Policies
Revenues									1,015,549
Selling, administrative, and other operating expenses									297,087
Loss from operations									45,546
Net income									37,269
Net income attributable to common stockholders									37,269
Other current assets	12,034								12,034
Deposits and other assets	47,701								47,701
Total assets	818,704								818,704
Deferred revenue	20,565								20,565
Total liabilities	183,978								183,978
Retained earnings (accumulated deficit)	22,507								22,507
Total stockholders’ equity	$ 633,425								$ 633,425

[1] Net income excludes $0.2 million and $0.9 million for the years ended June 30, 2018 and 2017, respectively, due to the redeemable noncontrolling interest related to Middlebury Interactive Languages and LearnBop, which is reported outside of permanent equity in the accompanying consolidated balance sheets (See Note 9, “Redeemable Noncontrolling Interest”).