Revenue Recognition - Schedule of Previously Reported Balances, Adjustment and Current Reported Balances (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Student receivables, net of allowance for doubtful accounts, current	$ 34,043		$ 18,875
Deferred revenue	$ 22,988	$ 29,560	$ 22,897
ASC Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Student receivables, net of allowance for doubtful accounts, current		25,538
Deferred revenue		29,560
Impact of Modified Retrospective Adoption of ASC 606 [Member] | ASC Topic 606 [Member]
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Student receivables, net of allowance for doubtful accounts, current		6,663
Deferred revenue		$ 6,663