Cash, Cash Equivalents and Marketable Securities Available for Sale - Summary of Cash, Cash Equivalents and Marketable Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Sep. 30, 2016
Cash and Cash Equivalents
Cash, cash equivalents and marketable securities [Line Items]
Amortized Cost	$ 105,618	$ 75,926
Gross Unrealized Gains	0	0
Fair Value	105,618	75,926
Cash and Cash Equivalents \| Cash
Cash, cash equivalents and marketable securities [Line Items]
Amortized Cost	90,323	75,486
Gross Unrealized Gains	0	0
Fair Value	90,323	75,486
Cash and Cash Equivalents \| Money market funds
Cash, cash equivalents and marketable securities [Line Items]
Amortized Cost	6,471	440
Gross Unrealized Gains	0	0
Fair Value	6,471	440
Cash and Cash Equivalents \| Bank Time Deposits
Cash, cash equivalents and marketable securities [Line Items]
Amortized Cost	8,824	0
Gross Unrealized Gains	0	0
Fair Value	8,824	0
Long-term Marketable Securities \| Marketable equity securities
Cash, cash equivalents and marketable securities [Line Items]
Amortized Cost	10,788	9,598
Gross Unrealized Gains	3,003	1,418
Fair Value	$ 13,791	$ 11,016

Cash, cash equivalents and marketable securities

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- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

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- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

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- Definition

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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