Restructuring and Other Charges, net (Additional Information) (Detail) $ in Thousands	3 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Sep. 30, 2020 USD ($)
Other Restructuring [Member] | Corporate | Stand-up and separation [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 700
Restructuring Charges and Other Expenses	8,566	$ 6,683
Restructuring Reserve	$ 18,136		$ 16,857
Document Fiscal Year Focus	2021
Restructuring charges	$ 7,860	$ 4,048
Restructuring and Related Cost, Expected Number of Positions Eliminated	57	37
Personnel
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	$ 2,067		1,243
Restructuring charges	4,789	$ 2,913
Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	16,069		$ 15,614
Restructuring charges	3,071	1,135
Other Expense [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring charges		2,800
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring Charges and Other Expenses	1,684	2,436
Restructuring charges	978	(199)
Corporate | Personnel
Restructuring Cost and Reserve [Line Items]
Restructuring charges	975	333
Corporate | Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 3	$ (532)