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Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Apr. 12, 2019	Mar. 31, 2018
Subsequent Event [Line Items]
Stock issued during period, shares, new issues		22,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Stock issued during period, shares, new issues	5,670,000
Sale of stock, price per share	$ 11
Proceeds from issuance common stock before underwriters discounts and commissions and offering expenses	$ 85.8
Pre Funded Warrant [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Class of warrant or right, warrants to purchase of common stock	2,130,000
Class of warrant or right, exercise price of warrants or rights	$ 10.999
Class A Warrant [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Class of warrant or right, warrants to purchase of common stock	3,900,000
Class of warrant or right, exercise price of warrants or rights	$ 13.20
Class of warrants or rights expiration period	5 years

X

- Definition

Exercise price per share or per unit of warrants or rights outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(4))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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Balance Type:	na
Period Type:	instant

X

- Definition

Number of securities into which the class of warrant or right may be converted. For example, but not limited to, 500,000 warrants may be converted into 1,000,000 shares.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(i)(2))
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690

+ Details

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X

- Definition

Per share amount received by subsidiary or equity investee for each share of common stock issued or sold in the stock transaction.

+ References

No definition available.

+ Details

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X

- Definition

Number of new stock issued during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=109259400&loc=d3e21463-112644

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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X

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

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X

- Definition

Class Of Warrant Or Right Warrants Expiration Period

+ References

No definition available.

+ Details

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X

- Definition

Proceeds From Issuance Of Common Stock Before Underwriting Discounts Commissions And Other Expenses

+ References

No definition available.

+ Details

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- Details

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- Details

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- Details

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