Restructuring and Other Charges, net (Additional Information) (Detail) $ in Thousands	3 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2018 USD ($)
Restructuring Cost and Reserve [Line Items]
Document Period End Date	Dec. 31, 2018
Restructuring Charges and Other Expenses	$ 23,081	$ 13,569
Restructuring Reserve	$ 15,040		$ 16,935
Document Fiscal Year Focus	2019
Restructuring charges	$ 10,389	$ 5,316
Number of personnel eliminated	131	160
Professional service fees	$ 78	$ 511
Tangible Asset Impairment Charges		6,000
Personnel
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	8,314		9,320
Restructuring charges	8,483	3,660
Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring Reserve	6,726		$ 7,615
Restructuring charges	1,906	1,656
Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Other Charges	12,692	8,253
Corporate
Restructuring Cost and Reserve [Line Items]
Restructuring Charges and Other Expenses	6,934	7,998
Restructuring charges	863	(255)
Corporate | Personnel
Restructuring Cost and Reserve [Line Items]
Restructuring charges	1,153	485
Corporate | Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring charges	(290)	(740)
Corporate | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Other Charges	6,071	8,253
Corporate | Chief Executive Officer [Member] | Other Restructuring [Member]
Restructuring Cost and Reserve [Line Items]
Other Charges	$ 7,200	$ 2,300