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Number of milestone event probable of occurrence or achieved.

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Potential milestone payments receivable.

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Premium from sale of stock.

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Revenue performance obligation upfront payment received.

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Upfront license fee including premium of sale of stock.

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For an unclassified balance sheet, the amount due from customers or clients for goods or services that have been delivered or sold in the normal course of business, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection.

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Amount of obligation to transfer good or service to customer for which consideration has been received or is receivable.

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Amount of assets classified as other.

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Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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Represents the value established as the selling price of the significant unit of accounting used to allocate the consideration of the multiple-deliverable arrangement.

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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.

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Amount of transaction price allocated to performance obligation that has not been recognized as revenue.

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Year in which remaining performance obligation is expected to be recognized, in CCYY format.

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Revenue Recognition - Additional Information (Detail) ¥ in Billions		1 Months Ended		3 Months Ended	6 Months Ended
	May 17, 2018 USD ($) PerformanceObligation	Apr. 30, 2013 USD ($) PerformanceObligation	Apr. 30, 2012 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2018 USD ($) PerformanceObligation Milestone	Jun. 30, 2017 USD ($) Milestone	Dec. 31, 2017 USD ($)	Apr. 30, 2013 JPY (¥)
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Deferred revenue, current				$ 22,270,000	$ 22,270,000
Deferred revenue, non current				30,299,000	30,299,000
Total revenue				2,874,000	2,874,000	$ 911,000
Remaining performance obligations				0	$ 0
Number of milestone event probable of occurrence or achieved \| Milestone					0	0
License and Milestone Fees [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue				2,874,000	$ 2,874,000	$ 530,000
Royalty [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Revenue from contract with customer					0
VFMCRP Agreement [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Deferred revenue, current				22,270,000	22,270,000
Deferred revenue, non current				30,299,000	30,299,000
Receivables				0	0
Other assets				0	0
Deferred revenue	$ 55,444,000
Number of combined performance obligations for revenue recognized \| PerformanceObligation	1
Remaining performance obligations				$ 52,569,000	$ 52,569,000
Number of performance obligations for revenue recognized \| PerformanceObligation	2
Upfront payment	$ 50,000,000
Premium from sale of stock	$ 5,444,000
Remaining performance obligation, expected timing of satisfaction, year				2020	2020
VFMCRP Agreement [Member] \| License and Milestone Fees [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Total revenue					$ 2,874,000
Maruishi and CKDP Agreements [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Receivables				$ 0	0		$ 0
Other assets				0	0		0
Deferred revenue				$ 0	$ 0		$ 0
Maruishi Agreement [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Number of performance obligations for revenue recognized \| PerformanceObligation		2			2
Premium from sale of stock		$ 337,000
Upfront non-refundable, non-creditable license fee and premium from sale of stock		15,337,000
Maruishi Agreement [Member] \| Clinical Development and Regulatory Milestones [Member] \| Maximum [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Remaining potential consideration		10,500,000
Maruishi Agreement [Member] \| One-time Sales Milestone [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Remaining potential consideration \| ¥								¥ 1
Maruishi Agreement [Member] \| License [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Remaining performance obligations		9,637,000
Estimated selling price		10,200,000
Maruishi Agreement [Member] \| R&D Services [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Remaining performance obligations		5,700,000
Estimated selling price		$ 6,200,000
CKDP Agreement [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Premium from sale of stock			$ 83,000
CKDP Agreement [Member] \| Clinical Development and Regulatory Milestones [Member] \| Maximum [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Remaining potential consideration			3,750,000
CKDP Agreement [Member] \| License [Member]
Revenue Recognition Multiple Deliverable Arrangements [Line Items]
Revenue from contract with customer			$ 646,000