Restructuring Expenses - Summary of Restructuring Accruals and Certain Facility Closures (Detail) - USD ($)		3 Months Ended
	Oct. 01, 2019	Dec. 31, 2019	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Accrual at September 30, 2017	$ 1,378,000	$ 1,378,000
Expense Additions		3,104,000	$ 0
Cash Payments		(1,105,000)
Restructuring Reserve, Accrual Adjustment		(1,378,000)
Accrual at June 30, 2018		1,999,000
Reclassification of accrued lease exit obligations to operating lease liabilities		1,378,000
Reclassification of accrued lease exit obligations to operating lease liabilities		97,081,000
Facilities charges
Restructuring Reserve [Roll Forward]
Accrual at September 30, 2017	1,378,000	1,378,000
Expense Additions		0
Cash Payments		0
Restructuring Reserve, Accrual Adjustment		(1,378,000)
Accrual at June 30, 2018		0
Reclassification of accrued lease exit obligations to operating lease liabilities		1,378,000
Employee separation
Restructuring Reserve [Roll Forward]
Accrual at September 30, 2017	0	0
Expense Additions		3,104,000
Cash Payments		(1,105,000)
Restructuring Reserve, Accrual Adjustment		0
Accrual at June 30, 2018		1,999,000
Reclassification of accrued lease exit obligations to operating lease liabilities		$ 0
Accounting Standards Update 2016-02
Restructuring Reserve [Roll Forward]
Reclassification of accrued lease exit obligations to operating lease liabilities	98,900,000
Accounting Standards Update 2016-02 | Facilities charges
Restructuring Reserve [Roll Forward]
Restructuring Reserve, Accrual Adjustment	(1,400,000)
Reclassification of accrued lease exit obligations to operating lease liabilities	1,400,000
Reclassification of accrued lease exit obligations to operating lease liabilities	$ 1,400,000