Marketable Securities and Cash Equivalents - Summary of Marketable Securities and Cash Equivalents (Detail) $ in Thousands	Mar. 31, 2018 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 64,585
Unrealized Losses	(12)
Fair Value	64,573
Cash Equivalents [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	22,576
Unrealized Losses	(1)
Fair Value	22,575
Cash Equivalents [Member] \| Money Market Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	6,785
Fair Value	6,785
Cash Equivalents [Member] \| Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	2,010
Unrealized Losses	(1)
Fair Value	2,009
Cash Equivalents [Member] \| Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	13,781
Fair Value	13,781
Marketable Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	42,009
Unrealized Losses	(11)
Fair Value	41,998
Marketable Securities [Member] \| Corporate Debt Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	6,227
Unrealized Losses	(10)
Fair Value	6,217
Marketable Securities [Member] \| Commercial Paper [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	21,841
Fair Value	21,841
Marketable Securities [Member] \| Government Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	13,941
Unrealized Losses	(1)
Fair Value	$ 13,940

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

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- Definition

This item represents the cost of debt 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 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 2: 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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- Definition

Amount of debt 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 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 320
-Section 50
-Paragraph 2
-Subparagraph (b)-(g)
-URI http://asc.fasb.org/extlink&oid=75019621&loc=d3e62557-112803

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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