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Summary of Significant Accounting Policies (Narrative) (Details) shares in Millions, $ in Millions		12 Months Ended
	Dec. 29, 2016	Dec. 31, 2017 USD ($) segment shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 shares
Property, Plant and Equipment [Line Items]
Potentially dilutive common shares related to the outstanding preferred stock, stock options, restricted stock units and warrants \| shares		13.6	10.7	10.0
Number of operating segments (segment) \| segment		1
Minimum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of the assets		2 years
Maximum [Member]
Property, Plant and Equipment [Line Items]
Estimated useful lives of the assets		7 years
4550 Towne Centre Court, San Diego, California [Member]
Property, Plant and Equipment [Line Items]
Term of lease agreement	10 years	5 years
Financial Standby Letter of Credit [Member] \| Letter of Credit [Member] \| 4550 Towne Centre Court, San Diego, California [Member]
Property, Plant and Equipment [Line Items]
Stand by letter of credit		$ 0.9
Cash collateral as security		$ 0.9	$ 0.2