Summary of Significant Accounting Policies - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Concentration Risk [Line Items]
Deferred tax assets, net	$ 0	$ 0		$ 0
Uncertain tax positions	0	0		0
Right of use asset - operating lease	4,403,000	4,403,000	$ 4,452,000
Lease liabilities - operating lease	5,201,000	5,201,000
Lease liability, current - operating lease	198,000	198,000	111,000
Deferred rent - current				150,000
Lease liability, operating lease	$ 5,003,000	$ 5,003,000	5,156,000
Deferred rent - long term				$ 665,000
Accounting Standards Update 2016-02
Concentration Risk [Line Items]
Right of use asset - operating lease			4,452,000
Lease liabilities - operating lease			5,300,000
Lease liability, current - operating lease			111,000
Deferred rent - current			(150,000)
Lease liability, operating lease			5,156,000
Deferred rent - long term			$ (665,000)
License And Development Service Revenue | Revenue from Contract with Customer Benchmark | Collaboration Partner Concentration Risk
Concentration Risk [Line Items]
Concentration risk (percentage)	100.00%	100.00%