Related Party Transactions (Details)					1 Months Ended		4 Months Ended	12 Months Ended
	Oct. 07, 2016 USD ($) shares	Aug. 21, 2016 shares	Oct. 21, 2014 $ / shares shares	Oct. 17, 2014	Aug. 31, 2016 USD ($) item	Jan. 31, 2016 USD ($) item	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) item $ / shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Related Party Transactions
Loss on extinguishment of debt								$ (246,000)
Due from related party							$ 486,000	612,000	$ 486,000
Amounts due to related parties							1,359,000	1,694,000	1,359,000
Research and development expense								25,437,000	19,233,000	$ 21,126,000
Non-cash compensation expense (income)								1,472,000	965,000	$ 1,761,000
Inventory, Net							5,069,000	9,837,000	$ 5,069,000
Common Stock
Related Party Transactions
Conversion of convertible promissory notes to common stock (in shares) | shares									1,361,009
Number of shares sold | shares									10,639	1,558
Global Foundries | Research and Development | Common Stock
Related Party Transactions
Non-cash compensation expense (income)								1,500,000	$ 965,000	$ 1,800,000
Freescale
Related Party Transactions
Due from related party							486,000	587,000	486,000
Amounts due to related parties							380,000	945,000	380,000
Rent paid								1,000,000	1,100,000	1,000,000
Inventory, Net							2,500,000	3,100,000	2,500,000	3,900,000
Related party sales								2,300,000	2,400,000	3,500,000
Freescale | Wafers
Related Party Transactions
Purchases								1,400,000	904,000
Product purchased which is included in inventory								638,000	505,000
Joint Development Agreement | Global Foundries
Related Party Transactions
Agreement Term				4 years
Period to Repurchase Shares			1 year
Period of possession of exclusive right to manufacture after qualification of device				3 years
Period of possession of exclusive right to manufacture after completion of device development work				4 years
Due from related party							0	25,000	0
Amounts due to related parties							$ 979,000	749,000	979,000
Purchase of research and development equipment								747,000	0
Research and development expense								$ 5,200,000	2,900,000	3,600,000
Number of milestones | item					3
First milestone payment due per the agreement					$ 569,000
Second milestone payment due per the agreement					650,000
Third milestone payment due per the agreement					406,000
Number of milestones achieved | item								2
Milestone revenue								$ 1,600,000	$ 0	$ 0
Joint Development Agreement | Global Foundries | Common Stock
Related Party Transactions
Number of shares sold | shares			461,538
Shares sold, price per share | $ / shares			$ 0.00026
Number of shares of common stock, vested | shares		211,538					153,846
Number of shares of common stock, unvested | shares							96,153		96,153
Estimated fair value of common stock per share | $ / shares							$ 8.29	$ 7.50	$ 8.29	$ 13.52
Joint Development Agreement | Global Foundries | Series B Redeemable Convertible Preferred Stock
Related Party Transactions
Number of shares sold | shares			192,307
Shares sold, price per share | $ / shares			$ 26.00
2016 Convertible Promissory Notes | Stockholders
Related Party Transactions
Debt instrument, aggregate amount						$ 5,000,000
Debt instrument, interest rate						5.00%
Debt instrument, convertible, equity issuance trigger						$ 5,000,000
Debt instrument, threshold percentage						80.00%
Multiple factor for cash payment | item						3
Debt instrument, carrying value	$ 5,200,000
Unamortized discount	74,000
Derivative liability	70,000
Loss on extinguishment of debt	0
2016 Convertible Promissory Notes | Stockholders | Common Stock
Related Party Transactions
Accrued interest	$ 176,000
Conversion of convertible promissory notes to common stock (in shares) | shares	808,747
2016 Bridge Notes | Stockholders
Related Party Transactions
Debt instrument, aggregate amount					$ 3,500,000
Debt instrument, interest rate					5.00%
Debt instrument, convertible, equity issuance trigger					$ 5,000,000
Debt instrument, threshold percentage					80.00%
Multiple factor for cash payment | item					3
Debt instrument, carrying value	$ 3,500,000
Unamortized discount	122,000				$ 264,000	$ 653,000
Derivative liability	50,000
Loss on extinguishment of debt	0
2016 Bridge Notes | Stockholders | Common Stock
Related Party Transactions
Accrued interest	$ 35,000
Conversion of convertible promissory notes to common stock (in shares) | shares	552,262