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Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 12 Months Ended
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Dec. 31, 2014 | Dec. 31, 2013 | Dec. 31, 2012
Operating Leased Assets [Line Items] |  |  |
Lease agreement description | During 2014, the Company exercised its 5-year renewal option on the manufacturing facility. The Company also entered into a new four-year lease for additional space in the manufacturing facility effective April 1, 2014. This lease also has an option to continue the lease for five years under the same terms. |  |
Deferred rent liability | $ 2.7 us-gaap_DeferredRentCredit | $ 2.9 us-gaap_DeferredRentCredit |
Rent expense | $ 2.0 us-gaap_OperatingLeasesRentExpenseNet | $ 2.7 us-gaap_OperatingLeasesRentExpenseNet | $ 2.7 us-gaap_OperatingLeasesRentExpenseNet
Office and Laboratory Space [Member] | Rockville, Maryland [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Lease expiration date | Mar. 31, 2018 |  |
Amended lease expiration date | Jan. 31, 2020 |  |
Office and Laboratory Space [Member] | South San Francisco [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Lease expiration date | Feb. 28, 2018 |  |
Manufacturing Space [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Lease expiration date | Dec. 31, 2014 |  |
Lessee leasing arrangements, operating leases, renewal term | 5 years |  |
Additional Manufacturing Space [Member] |  |  |
Operating Leased Assets [Line Items] |  |  |
Term of additional space lease | 4 years |  |
Origination date for additional space in manufacturing facility | Apr. 01, 2014 |  |

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- Definition Lease Agreement Initiation Date + References No definition available. + Details
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- Definition The cumulative difference between the rental payments required by a lease agreement and the rental income or expense recognized on a straight-line basis, or other systematic and rational basis more representative of the time pattern in which use or benefit is granted or derived from the leased property, expected to be recognized in income or expense over the term of the leased property by the lessor or lessee, respectively. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 25 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=7501430&loc=d3e39896-112707 + Details
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- Definition A general description of the nature of the existing leasing arrangements of a lessee for all operating leases including, but not limited to: (1) rental escalation clauses; (2) renewal or purchase options; (3) guarantees or indemnities, if any, (4) restrictions imposed by lease arrangements; (5) unusual provisions or conditions; (6) contingent rentals, if any; and (7) lease expiration dates. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6452660&loc=d3e36991-112694 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 10 -Section 55 -Paragraph 40 -Subparagraph (Note 1) -URI http://asc.fasb.org/extlink&oid=6584154&loc=d3e38371-112697 + Details
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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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- Definition Term of the lessee's leasing arrangement renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Term of the lessee's leasing arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
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- Definition Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 840 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6453985&loc=d3e41499-112717 + Details
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