Condensed Financial Information of Registrant (Parent Company Only) - Schedule of Balance Sheets (Detail) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022	Sep. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021
Non-current assets:
Total assets	$ 2,383,978		$ 2,383,091
LIABILITIES AND STOCKHOLDERS' EQUITY:
Total liabilities	948,905		938,648
Stockholders' equity:
Preferred stock, $0.001 par value; 1,000,000 shares authorized and no shares issued or outstanding at December 31, 2022 and September 30, 2022, respectively
Additional paid‑in capital	1,641,321		1,630,378
Accumulated deficit	(122,565)		(113,002)
Accumulated other comprehensive income (loss)	(3,262)
Total stockholders' equity	1,435,073	$ 1,412,772	1,444,443	$ 1,493,034	$ 1,451,151	$ 1,427,164
Total liabilities and stockholders' equity	2,383,978		2,383,091
Treasury stock, at cost, 4,469,330 and 4,116,570 shares at December 31, 2022 and September 30, 2022, respectively	80,576		73,088
Parent Company [Member]
Non-current assets:
Investments in subsidiaries	1,435,073		1,444,443
Total non-current assets	1,435,073		1,444,443
Total assets	1,435,073		1,444,443
Stockholders' equity:
Preferred stock, $0.001 par value; 1,000,000 shares authorized and no shares issued or outstanding at December 31, 2022 and September 30, 2022, respectively
Additional paid‑in capital	1,641,321		1,630,378
Accumulated deficit	(122,565)		(113,002)
Total stockholders' equity	1,435,073		1,444,443
Total liabilities and stockholders' equity	1,435,073		1,444,443
Treasury stock, at cost, 4,469,330 and 4,116,570 shares at December 31, 2022 and September 30, 2022, respectively	(80,576)		(73,088)
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