Guarantor and Non-Guarantor Subsidiaries Financial Information - Additional Information (Detail)	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
5.625% Senior Secured Notes
Condensed Financial Statements Captions [Line Items]
Interest rate	5.625%		5.625%
5.625% Senior Secured Notes | Acquisition Corp.
Condensed Financial Statements Captions [Line Items]
Interest rate	5.625%	5.625%
Due date of Senior Secured Notes	2022	2022
5.00% 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 | Acquisition Corp.
Condensed Financial Statements Captions [Line Items]
Interest rate	4.125%	4.125%
Due date of Senior Secured Notes	2024	2024
4.875% Senior Secured Notes due 2024 | Acquisition Corp.
Condensed Financial Statements Captions [Line Items]
Interest rate	4.875%	4.875%
Due date of Senior Secured Notes	2024	2024
6.75% Senior Notes due 2022 | Acquisition Corp.
Condensed Financial Statements Captions [Line Items]
Interest rate	6.75%
Due date of Senior Secured Notes	2022