Summary of Significant Accounting Policies Narrative (Details)		12 Months Ended
	Jan. 01, 2012	Dec. 31, 2017 USD ($) Segment $ / shares	Dec. 31, 2016 USD ($) $ / shares	Dec. 31, 2015 USD ($)	Sep. 03, 2009 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Fair market value of options granted (usd per share) | $ / shares		$ 2.12	$ 3.66
Cumulative effect from adoption of new accounting standard				$ 0
Number of operating segments | Segment		1
Federal insurance coverage on operating cash		$ 250,000
Intangible assets		0	$ 0		$ 6,300,000
Finite-lived intangible assets useful life (years)	12 years
Amortization expense			200,000
Intangible asset impairment		0	3,905,000
Uncertain tax positions		$ 0	0
Additional paid-in capital
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect from adoption of new accounting standard				$ (100,000)
New Accounting Pronouncement, Early Adoption, Effect | Accounting Standards Update 2016-09 | Accumulated deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect from adoption of new accounting standard			$ 100,000