Income Taxes - Narrative (Details)	12 Months Ended			137 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2017 USD ($) ownership_change	Dec. 31, 2011 USD ($)	Aug. 31, 2006 USD ($)
Operating Loss Carryforwards [Line Items]
Penalties and interest expense	$ 0	$ 0	$ 0
Penalties and interest accrued	0	0		$ 0
Number of changes in ownership | ownership_change				3
Foreign rate change - Impact on Deferred Taxes	36,085,000	0	0
Less valuation allowance	101,114,000	112,322,000		$ 101,114,000
Income tax expense (benefits)	0	(948,000)	(15,901,000)
Refundable cash credit claim	3,100,000			3,100,000
Internal Revenue Service (IRS) [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses	254,400,000			254,400,000
Tax credit carryforward, amount	3,300,000			3,300,000
Operating loss carryforwards decrease					$ 121,100,000	$ 1,900,000
Tax credit carryforwards, decrease					3,000,000	$ 8,000
State and Local Jurisdiction [Member]
Operating Loss Carryforwards [Line Items]
Tax credit carryforward, amount	4,000,000			4,000,000
Operating loss carryforwards decrease					$ 53,300,000
State and Local Jurisdiction [Member] | California [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses	192,600,000			192,600,000
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Net operating losses	135,700,000			$ 135,700,000
Zohydro ER [Member]
Operating Loss Carryforwards [Line Items]
Tax effect of sale of discontinued operation	(71,000)	(88,000)	14,060,000
Zogenix International Limited [Member]
Operating Loss Carryforwards [Line Items]
Income tax expense (benefits)	$ 0	$ (1,000,000)	$ (2,100,000)