Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019
Concentration Risk [Line Items]
Impairment of long-lived assets	$ 0	$ 1,116,000	$ 8,431,000
Total revenue	0	9,821,000	28,850,000
Deferred tax asset	118,538,000	101,114,000
Less valuation allowance	118,064,000	101,114,000
Long Lived Assets, Production [Member] | Sumavel DosePro [Member]
Concentration Risk [Line Items]
Impairment of long-lived assets		$ 800,000	$ 6,400,000
ZX008 [Member]
Concentration Risk [Line Items]
Potential contingent payment, minimum	0
Potential contingent payment, maximum	$ 95,000,000.0
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member] | Minimum [Member]
Concentration Risk [Line Items]
Right of use asset				$ 7,500,000
Lease liability				12,000,000.0
Subsequent Event [Member] | Accounting Standards Update 2016-02 [Member] | Maximum [Member]
Concentration Risk [Line Items]
Right of use asset				9,500,000
Lease liability				$ 14,000,000.0