Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Income Taxes [Line Items]
Undistributed earnings of foreign subsidiaries		$ 52,000	$ 40,300	$ 25,200
Long-term deferred tax liabilities		2,913	3,495
Establishment of a valuation allowance	$ 79,300	77,531	(36)	453
Deferred tax asset			83,638
Federal research and development tax credit carryforwards		$ 18,700
Federal research and development tax credit carryforwards, expiration year		2036
Understatement of gross deferred tax assets operating loss carryforwards and related valuation allowance			12,900
Unrecognized tax benefits		$ 3,800
Interest related to unrecognized benefits		100	200	300
Reductions from lapses in statutes of limitations		897	734	$ 861
Minimum
Income Taxes [Line Items]
Anticipated unrecognized tax benefit reduction during next twelve months		1,100
Federal
Income Taxes [Line Items]
Net operating loss carryforwards		137,000
State
Income Taxes [Line Items]
Net operating loss carryforwards		114,000
Foreign
Income Taxes [Line Items]
Net operating loss carryforwards		85,000
Stock Compensation Plan
Income Taxes [Line Items]
Net operating loss carryforwards		15,000
State Credit Carryforward
Income Taxes [Line Items]
State research and development tax credit carryforwards		10,400
Accounting Standards Update 2015-17 | New Accounting Pronouncement, Early Adoption, Effect
Income Taxes [Line Items]
Current deferred tax assets		(17,600)	17,600
Non-current deferred tax assets		16,700	70,500
Current deferred tax liabilities		(1,300)	1,300
Long-term deferred tax liabilities		$ 300	$ 3,200