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, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares	Dec. 31, 2014 USD ($) $ / shares shares	Aug. 31, 2014 USD ($)
Related Party Transactions
Debt instrument, convertible, equity issuance trigger								$ 5,000,000
Amounts due to related parties							$ 1,359,000	1,359,000	$ 3,812,000
Research and development expense								19,233,000	21,126,000	$ 12,664,000
Non-cash compensation expense (income)								965,000	1,761,000	107,000
Processing cost							5,069,000	5,069,000	4,176,000
Related party sales								2,378,000	3,472,000	$ 3,191,000
Due from related party							486,000	$ 486,000	564,000
Common Stock
Related Party Transactions
Conversion of convertible promissory notes (in shares) | shares								1,361,009
Number of shares sold | shares										9,848
Redeemable Convertible Preferred Stock
Related Party Transactions
Conversion of convertible promissory notes (in shares) | shares										77,518
Number of shares sold | shares										385,641
Global Foundries | Common Stock
Related Party Transactions
Number of shares sold | shares										461,538
Global Foundries | Research and Development | Common Stock
Related Party Transactions
Non-cash compensation expense (income)								$ 965,000	1,800,000	$ 107,000
Freescale
Related Party Transactions
Amounts due to related parties							380,000	380,000	207,000
Rent paid								1,100,000	1,000,000	1,000,000
Processing cost							2,500,000	2,500,000	3,900,000	3,300,000
Related party sales								2,400,000	3,500,000	3,200,000
Due from related party							486,000	486,000	564,000
Joint Development Agreement | Global Foundries
Related Party Transactions
Amounts due to related parties							$ 979,000	979,000	3,500,000
Research and development expense								$ 2,900,000	$ 3,600,000	$ 0
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
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					38,462
Number of shares of common stock, unvested | shares							211,538	211,538
Estimated fair value of common stock per share | $ / shares							$ 8.29	$ 8.29	$ 13.52	$ 4.68
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
2014 Convertible Promissory Notes | Stockholders
Related Party Transactions
Debt instrument, aggregate amount											$ 2,000,000
2014 Convertible Promissory Notes | Stockholders | Series B Redeemable Convertible Preferred Stock
Related Party Transactions
Accrued interest	$ 2,000,000
Conversion of convertible promissory notes (in shares) | shares	77,518
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%
Debt instrument, carrying value	$ 5,200,000
Unamortized discount	74,000
Derivative liability	70,000
Gain or loss from extinguishment of debt	0
Multiple factor for cash payment | item						3
2016 Convertible Promissory Notes | Stockholders | Common Stock
Related Party Transactions
Accrued interest	$ 176,000
Conversion of convertible promissory notes (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%
Debt instrument, carrying value	$ 3,500,000
Unamortized discount	122,000				$ 264,000	$ 653,000
Derivative liability	50,000
Gain or loss from extinguishment of debt	0
Multiple factor for cash payment | item					3
2016 Bridge Notes | Stockholders | Common Stock
Related Party Transactions
Accrued interest	$ 35,000
Conversion of convertible promissory notes (in shares) | shares	552,262