Guarantor and Non-Guarantor Subsidiaries Financial Information - Additional Information (Detail)				12 Months Ended
	Oct. 12, 2018	Oct. 09, 2018	Mar. 14, 2018	Sep. 30, 2019	Apr. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
5.000% Senior Secured Notes due 2023 | Acquisition Corp.
Condensed Financial Statements, Captions [Line Items]
Interest rate				5.00%
Due date of Senior Secured Notes				2023
4.125% Senior Secured Notes due 2024
Condensed Financial Statements, Captions [Line Items]
Interest rate				4.125%		4.125%	4.125%
4.125% Senior Secured Notes due 2024 | Acquisition Corp.
Condensed Financial Statements, Captions [Line Items]
Interest rate	4.125%	4.125%		4.125%
Due date of Senior Secured Notes	2024			2024
4.875% Senior Secured Notes
Condensed Financial Statements, Captions [Line Items]
Interest rate				4.875%		4.875%	4.875%
4.875% Senior Secured Notes | Acquisition Corp.
Condensed Financial Statements, Captions [Line Items]
Interest rate		4.875%		4.875%
Due date of Senior Secured Notes		2024		2024
3.625% Senior Secured Notes due 2026
Condensed Financial Statements, Captions [Line Items]
Interest rate				3.625%		3.625%	3.625%
3.625% Senior Secured Notes due 2026 | Acquisition Corp.
Condensed Financial Statements, Captions [Line Items]
Interest rate		3.625%		3.625%	3.625%
Due date of Senior Secured Notes		2026		2026
5.500% Senior Notes due 2026
Condensed Financial Statements, Captions [Line Items]
Interest rate				5.50%		5.50%	5.50%
5.500% Senior Notes due 2026 | Acquisition Corp.
Condensed Financial Statements, Captions [Line Items]
Interest rate			5.50%	5.50%
Due date of Senior Secured Notes			2026	2026