Summary of Significant Accounting Policies and Select Balance Sheet Information - Additional Information (Detail) - USD ($) shares in Millions	3 Months Ended								9 Months Ended	12 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2013	Sep. 30, 2006	Oct. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Net unrealized loss reclassified out of accumulated other comprehensive income (loss) with a corresponding adjustment to other income (loss)										$ 0	$ 0	$ 0
Held-to-maturity debt securities	$ 0				$ 0				$ 0	0	0
Realized gains or losses on sales of available-for-sale securities										0	0	0
Depreciation expense										4,700,000	3,700,000	3,000,000
Amortization expense									2,700,000	2,600,000		2,600,000
Impairment loss											0
Other impairment losses										0		0
Goodwill impairment charges										0	0	0
Goodwill	26,171,000				27,032,000				27,032,000	26,171,000	27,032,000	27,282,000
Goodwill subject to revaluation due to fluctuations in exchange rates	13,400,000									13,400,000
Impairment charges relating to long-lived assets										$ 0	$ 0	$ 0
Sales-based and minimum royalties due period										45 days
Weighted average diluted shares outstanding excluded outstanding stock options										0.2	1.0	0.2
Revenue	30,816,000	$ 24,344,000	$ 22,676,000	$ 22,241,000	23,038,000	$ 22,227,000	$ 19,058,000	$ 17,013,000		$ 100,077,000	$ 81,336,000	$ 73,112,000
Income tax benefit										(34,000)	$ (3,075,000)	$ 3,107,000
Deferred rent liability	1,200,000									1,200,000
ASC Topic 842 [Member] | Scenario Forecast [Member]
Summary Of Significant Accounting Policies [Line Items]
Right of use asset															$ 1,700,000
Lease obligation liability															$ 2,900,000
Impact of Adoption [Member] | Adoption of ASC Topic 606 [Member]
Summary Of Significant Accounting Policies [Line Items]
Revenue										$ 1,300,000
Type of Revenue [Extensible List]										us-gaap:RoyaltyMember
Customer Concentration Risk [Member] | Revenue [Member] | Abbott [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue										19.00%	11.00%
Customer Concentration Risk [Member] | Revenue [Member] | Medtronic [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue										14.00%	16.00%	18.00%
SurVeil DCB [Member] | Product Concentration Risk | Revenue [Member] | Abbott [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue										13.00%	5.00%	0.00%
Abbott [Member]
Summary Of Significant Accounting Policies [Line Items]
Upfront fee received										$ 25,000,000	$ 25,000,000
Collaborative arrangement milestone payment received										10,000,000
Abbott [Member] | TRANSCEND Clinical Trial [Member]
Summary Of Significant Accounting Policies [Line Items]
Collaborative arrangement milestone payment received										$ 10,000,000
Abbott [Member] | SurVeil DCB [Member]
Summary Of Significant Accounting Policies [Line Items]
Clinical study completion period										6 years
IDA [Member]
Summary Of Significant Accounting Policies [Line Items]
Reimbursement recorded as reduction to R&D expense										$ 700,000	800,000	$ 800,000
Research and development [Member] | In-Process Research and Development [Member]
Summary Of Significant Accounting Policies [Line Items]
Impairment loss										300,000		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				5,300,000		5,300,000
Impairment loss on investment													$ 100,000	$ 4,700,000
Cost method of investment					$ 500,000				$ 500,000		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
Payment period set for R&D services										45 days
Maximum [Member] | Impact of Adoption [Member] | Adoption of ASC Topic 606 [Member]
Summary Of Significant Accounting Policies [Line Items]
Income tax benefit										$ 300,000
Maximum [Member] | Customer Concentration Risk [Member] | Revenue [Member] | Medtronic [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue										10.00%
Maximum [Member] | Product Concentration Risk | Revenue [Member] | Medtronic [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of revenue										3.00%
Maximum [Member] | Abbott [Member]
Summary Of Significant Accounting Policies [Line Items]
Collaborative arrangement additional potential milestone payments receivable	$ 57,000,000									$ 57,000,000
Maximum [Member] | ViaCyte, Inc. [Member]
Summary Of Significant Accounting Policies [Line Items]
Company's ownership percentage	1.00%									1.00%
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Product sales payment terms										30 days
Payment period set for R&D services										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.