Number of shares of equity interests issued or issuable to acquire entity.

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-SubTopic 30
-Section 50
-Paragraph 1
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- Definition

Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 55
-Paragraph 37
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- Definition

Face amount or stated value per share of common stock.

+ 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
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- Definition

The number of new shares issued in the conversion of stock in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-SubTopic 10
-Section 50
-Paragraph 5
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- Definition

Date which lease or group of leases is set to expire, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Future minimum rental payments in aggregate as of the balance sheet date under operating leases.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 4
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Period Type:	instant

- Definition

Description of the reverse stock split arrangement. Also provide the retroactive effect given by the reverse split that occurs after the balance sheet date but before the release of financial statements.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 4.C)
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- 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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- Definition

Area of facility lease.

+ References

No definition available.

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Balance Type:	na
Period Type:	duration

- Definition

Lease commencement date.

+ References

No definition available.

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Balance Type:	na
Period Type:	duration

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Subsequent Event - Additional Information (Detail) $ / shares in Units, $ in Millions			1 Months Ended	9 Months Ended
	Oct. 16, 2018	Oct. 12, 2018 USD ($) $ / shares shares	Oct. 31, 2018 USD ($) ft²	Sep. 30, 2018 $ / shares	Dec. 31, 2017 $ / shares
Subsequent Event [Line Items]
Common stock, par value \| $ / shares				$ 0.0001	$ 0.0001
Common Stock [Member]
Subsequent Event [Line Items]
Reverse stock split ratio				1-for-6
Subsequent Event [Member] \| 2479 E. Bayshore Blvd, Palo Alto, California [Member] \| Sublease Agreement [Member]
Subsequent Event [Line Items]
Lease commencement date			October 30, 2018
Office space lease area \| ft²			4,240
Lease expires date			Aug. 31, 2020
Sublease payment receivable \| $			$ 0.3
Subsequent Event [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Reverse stock split ratio	1-for-6
Subsequent Event [Member] \| Versartis [Member]
Subsequent Event [Line Items]
Common stock, par value \| $ / shares		$ 0.0001
Preliminary estimate of purchase price \| $		$ 54.2
Subsequent Event [Member] \| Versartis [Member] \| Common Stock [Member]
Subsequent Event [Line Items]
Shares issued upon conversion of stock		2.2801
Aggregate consideration issuable in merger, shares		30,851,600
Subsequent Event [Member] \| Versartis [Member] \| Options to Purchase Common Stock [Member]
Subsequent Event [Line Items]
Aggregate consideration issuable in merger, shares		7,103,859