Segment Reporting - Summary Financial Information by Reporting Segment (Parenthetical) (Detail) $ in Millions	Sep. 30, 2019 USD ($)
Segment Reporting Information [Line Items]
Settlement reserve	$ 7.1
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Settlement reserve	7.1
CTU [Member]
Segment Reporting Information [Line Items]
Settlement reserve	18.6
AIU [Member]
Segment Reporting Information [Line Items]
Settlement reserve	$ 11.4