Commitments And Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018 USD ($) ft² $ / mo	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Jul. 01, 2017	Jan. 31, 2017 ft²
Commitments and Contingencies [Line Items]
Rent expense, including common area maintenance charges | $	$ 0.2	$ 0.3	$ 0.2
Burlingame, CA [Member]
Commitments and Contingencies [Line Items]
Lease expiration date	Jun. 30, 2017
Area Of Lease | ft²	4,300
Monthly Expense, Operating Leases | $ / mo	21,000
Hayward, CA [Member]
Commitments and Contingencies [Line Items]
Lease expiration date	Aug. 31, 2022
Area Of Lease | ft²					15,700
Lease renewable term				5 months
Landlord [Member] | Hayward, CA [Member]
Commitments and Contingencies [Line Items]
Initial tenant leashold improvements | $	$ 2.1