Commitments and Contingencies - Narrative (Details)		1 Months Ended							12 Months Ended
	Jan. 01, 2017 USD ($)	May 31, 2017 USD ($) ft²	Jan. 31, 2017 USD ($)	Oct. 31, 2016 USD ($)	Jan. 31, 2016 ft²	Dec. 31, 2015 USD ($)	Jul. 31, 2015 USD ($)	Jan. 31, 2015 USD ($) ft²	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Other Commitments [Line Items]
Square footage leased | ft²					20,133			9,640
Term of lease	5 years
Optional lease extension period	3 years							5 years
Annual base rent	$ 1,100,000
Annual increase in base rent, percent	2.50%
Leasehold improvements									$ 183,000	$ 156,000
Accumulated depreciation									3,078,000	2,729,000
Payments for Deposits			$ 200,000
Funds drawn on letter of credit									0
Rent expense									1,500,000	713,000	$ 849,000
Sublease agreement, rentable square feet | ft²		5,048
Sublease agreement term		3 years
Sublease agreement, annual base rent		$ 273,000
Sublease agreement, annual base rent, percent		2.50%
Collaborative Arrangement | ZVex Product | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									7,700,000
Collaborative Arrangement | NanoPass Technologies LTD | Intradermal Delivery Device
Other Commitments [Line Items]
Collaborative arrangement, license fee						$ 500,000	$ 600,000
Collaborative arrangement, non-refundable deposit				$ 150,000
Collaborative Arrangement | NanoPass Technologies LTD | Intradermal Delivery Device | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to				$ 8,800,000
Collaborative Arrangement | Infectious Disease Research Institute | GLA/SLA First Exclusive Product | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									2,300,000
Collaborative Arrangement | Infectious Disease Research Institute | GLA/SLA Subsequent Exclusive Products | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									1,300,000
Collaborative Arrangement | Infectious Disease Research Institute | GLA/SLA First Non-Exclusive Product | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									1,300,000
Collaborative Arrangement | Infectious Disease Research Institute | GLA/SLA Subsequent Non-Exclusive Products | Maximum
Other Commitments [Line Items]
Potential future milestone payments, up to									625,000
Financial Standby Letter of Credit
Other Commitments [Line Items]
Letter of credit provided as security deposit								$ 121,000
Leasehold improvements
Other Commitments [Line Items]
Accumulated depreciation									$ 147,000	$ 123,000