Condensed Financial Information of Registrant (Parent Company Only) - Schedule of Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2019
Non-current assets:
Total assets	$ 2,383,091	$ 2,187,834	$ 1,931,856
LIABILITIES AND STOCKHOLDERS’ EQUITY:
Total liabilities	938,648	760,670
Stockholders’ equity:
Preferred stock, $0.001 par value; 1,000,000 shares authorized and no shares issued and outstanding at September 30, 2022 and September 30, 2021, respectively
Additional paid-in capital	1,630,378	1,615,236
Accumulated deficit	(113,002)	(188,227)
Treasury stock, at cost, 4,116,570 shares at September 30, 2022 and 0 shares at September 30, 2021	(73,088)
Total stockholders’ equity	1,444,443	1,427,164	$ 1,303,888	$ 490,023
Total liabilities and stockholders’ equity	2,383,091	2,187,834
Parent Company [Member]
Non-current assets:
Investments in subsidiaries	1,444,443	1,427,164
Total non-current assets	1,444,443	1,427,164
Total assets	1,444,443	1,427,164
Stockholders’ equity:
Preferred stock, $0.001 par value; 1,000,000 shares authorized and no shares issued and outstanding at September 30, 2022 and September 30, 2021, respectively
Additional paid-in capital	1,630,378	1,615,236
Accumulated deficit	(113,002)	(188,227)
Treasury stock, at cost, 4,116,570 shares at September 30, 2022 and 0 shares at September 30, 2021	(73,088)
Total stockholders’ equity	1,444,443	1,427,164
Total liabilities and stockholders’ equity	1,444,443	1,427,164
Common Class A [Member]
Stockholders’ equity:
Common stock value	155	155
Common Class A [Member] | Parent Company [Member]
Stockholders’ equity:
Common stock value	$ 155	$ 155