Summary of Significant Accounting Policies and Select Balance Sheet Information - Additional Information (Detail) - USD ($) shares in Millions		3 Months Ended	12 Months Ended
	Aug. 31, 2018	Mar. 31, 2013	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2006
Summary Of Significant Accounting Policies [Line Items]
Net unrealized loss reclassified out of accumulated other comprehensive income with a corresponding adjustment to other income (loss)			$ 0	$ 0	$ 0
Held-to-maturity debt securities			0	0
Realized gains or losses on sales of available-for-sale securities			0	0	0
Depreciation expense			3,700,000	3,000,000	2,300,000
Amortization expense			2,700,000	2,600,000	2,400,000
Impairment loss			0
Other impairment losses			0	0
Goodwill impairment charges	$ 0		0	0	0
Goodwill			27,032,000	27,282,000	26,555,000
Goodwill subject to revaluation due to fluctuations in exchange rates			13,400,000
Impairment charges relating to long-lived assets			0	0	0
Taxes collected from customers and remitted to governmental authorities			100,000	$ 100,000	$ 100,000
Weighted average diluted shares outstanding excluded outstanding stock options				0.2	0.7
Accounting Standards Update 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Estimated change to retained earnings due to adoption of new accounting standard			5,900,000
Contract asset			7,600,000
Deferred tax liabilities			1,700,000
IDA [Member]
Summary Of Significant Accounting Policies [Line Items]
Reimbursement recorded as reduction to R&D expense			$ 800,000	$ 800,000	$ 0
Customer Concentration Risk [Member] | Revenue [Member] | Medtronic [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue			16.00%	18.00%	25.00%
Customer Concentration Risk [Member] | Revenue [Member] | Abbott [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue			11.00%
Other Accrued Liabilities, Current and Other Long-term Liabilities [Member]
Summary Of Significant Accounting Policies [Line Items]
Deferred revenue			$ 20,900,000	$ 300,000
Medical Device [Member]
Summary Of Significant Accounting Policies [Line Items]
Goodwill			19,022,000	19,272,000	$ 18,545,000
Additions to goodwill					17,900,000
Research and development [Member] | In-Process Research and Development [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment loss				300,000
Selling, General and Administrative Expenses [Member] | In-Process Research and Development [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment loss				100,000
ViaCyte, Inc. [Member]
Summary Of Significant Accounting Policies [Line Items]
Equity method investment			5,300,000
Impairment loss on investment		$ 100,000				$ 4,700,000
Cost method of investment			500,000
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Revenue recognized from activity with companies in which it had strategic investment			$ 100,000	$ 100,000	$ 100,000
Product sales payment terms			45 days
Maximum [Member] | Customer Concentration Risk [Member] | Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue			10.00%
Maximum [Member] | Product Concentration Risk [Member] | Revenue [Member] | Medtronic [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue			4.00%
Maximum [Member] | ViaCyte, Inc. [Member]
Summary Of Significant Accounting Policies [Line Items]
Company's ownership percentage			1.00%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Product sales payment terms			30 days
Leasehold Improvements [Member]
Summary Of Significant Accounting Policies [Line Items]
Amortization period			Leasehold improvements are amortized over the shorter of the term of the lease or the estimated useful life of the asset.