Preferred Stock Warrant Liabilities - Additional Information (Details) - USD ($)		1 Months Ended								12 Months Ended
	Oct. 26, 2016	Jun. 30, 2015	Jun. 30, 2014	Apr. 30, 2013	Dec. 31, 2012	Nov. 30, 2012	Feb. 28, 2011	May 31, 2010	Nov. 30, 2009	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 27, 2013
Class Of Warrant Or Right [Line Items]
Change in fair value of preferred stock warrant liabilities										$ 2,123,000	$ 111,000	$ 291,000
CHCF Note
Class Of Warrant Or Right [Line Items]
Exercise price of warrants						$ 16.39
Fair value assumptions, expected volatility rate						60.00%
Fair value assumptions, risk free interest rate						1.60%
Fair value assumptions, expected term						10 years
Change in fair value of preferred stock warrant liabilities						$ 153,000				$ 50,000	14,000	24,000
Warrant exercise period										Oct. 03, 2016
Warrant [Member]
Class Of Warrant Or Right [Line Items]
Change in fair value of preferred stock warrant liabilities										$ 237,000	14,000	(4,000)
Warrant exercise period										Oct. 26, 2016
Issuance of common stock upon exercise of warrants, Shares	7,310
Fair value warrants recorded as debt discount			$ 98,000
Fair value assumptions, discount rate			30.00%
Warrant exercised	10,068
Warrants outstanding										10,068
Warrant [Member] | CHCF Note
Class Of Warrant Or Right [Line Items]
Change in fair value of preferred stock warrant liabilities										$ 19,000	6,000
Warrant exercise period										Oct. 03, 2016
Fair value warrants recorded as debt discount		$ 44,000
Warrant [Member] | CHCF Note | Minimum
Class Of Warrant Or Right [Line Items]
Fair value assumptions, discount rate		13.00%
Warrant [Member] | CHCF Note | Maximum
Class Of Warrant Or Right [Line Items]
Fair value assumptions, discount rate		27.00%
Series D Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares			20,136
Exercise price of warrants			$ 7.31
Series D Preferred Stock | CHCF Note
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares		8,552				22,807
Exercise price of warrants		$ 6.58
Series D Preferred Stock | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Warrants expiry period										Jun. 30, 2024
Series D Preferred Stock | Warrant [Member] | CHCF Note
Class Of Warrant Or Right [Line Items]
Description of warrants expiration period										expire at the earlier of November 2022 or a liquidation event
Series C Convertible Preferred Stock | CHCF Note
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares						150,000
Description of warrants expiration period										expire at the earlier of November 2022 or a liquidation event
Warrants issued to purchase preferred stock					9,152
Series C Convertible Preferred Stock | CHCF Note | Minimum
Class Of Warrant Or Right [Line Items]
Proceeds from issuance of warrants						$ 500,000
2009 Loan Agreement One | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Fair value assumptions, expected volatility rate									70.00%
Fair value assumptions, risk free interest rate									2.20%
Fair value assumptions, exercise price									$ 5.67
Fair value assumptions, expected term									10 years
Fair value warrants recorded as debt issuance cost									$ 68,000
Change in fair value of preferred stock warrant liabilities										$ 182,000	38,000	28,000
Warrant exercise period										Oct. 26, 2016
Issuance of common stock upon exercise of warrants, Shares	12,491
2009 Loan Agreement One | Series A Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares									15,865
Exercise price of warrants									$ 5.67
2009 Loan Agreement One | Series A Convertible Preferred Stock | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Warrants expiry period										Nov. 30, 2019
2009 Loan Agreement Two | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Fair value assumptions, expected volatility rate									70.00%
Fair value assumptions, risk free interest rate									2.20%
Fair value assumptions, exercise price									$ 5.67
Fair value assumptions, expected term									10 years
Change in fair value of preferred stock warrant liabilities										$ 101,000	22,000	15,000
Warrant exercise period										Oct. 26, 2016
Issuance of common stock upon exercise of warrants, Shares	6,939
Fair value warrants recorded as debt discount									$ 38,000
2009 Loan Agreement Two | Series A Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares									8,813
Exercise price of warrants									$ 5.67
2009 Loan Agreement Two | Series A Convertible Preferred Stock | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Warrants expiry period										Nov. 30, 2019
2010 Loan Agreement | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Fair value assumptions, expected volatility rate								60.00%
Fair value assumptions, risk free interest rate								2.80%
Fair value assumptions, exercise price								$ 16.39
Fair value assumptions, expected term								9 years 6 months
Change in fair value of preferred stock warrant liabilities										$ 14,000	5,000	4,000
Warrant exercise period										Oct. 26, 2016
Issuance of common stock upon exercise of warrants, Shares	2,119
Fair value warrants recorded as debt discount								$ 19,000
2010 Loan Agreement | Series B Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares								1,525
Exercise price of warrants								$ 16.39
2010 Loan Agreement | Series B Convertible Preferred Stock | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Warrants expiry period										Nov. 30, 2019
2011 Loan Agreement | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Fair value assumptions, expected volatility rate							60.00%
Fair value assumptions, risk free interest rate							3.40%
Fair value assumptions, exercise price							$ 16.39
Fair value assumptions, expected term							10 years
Change in fair value of preferred stock warrant liabilities										$ 104,000	42,000	29,000
Warrant exercise period										Oct. 26, 2016
Issuance of common stock upon exercise of warrants, Shares	16,113
Fair value warrants recorded as debt discount							$ 121,000
2011 Loan Agreement | Series B Convertible Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares							11,592
Exercise price of warrants							$ 16.39
2011 Loan Agreement | Series B Convertible Preferred Stock | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Warrants expiry period										Feb. 28, 2021
2012 Loan Agreement
Class Of Warrant Or Right [Line Items]
Exercise price of warrants						$ 0.01
2012 Loan Agreement | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Change in fair value of preferred stock warrant liabilities										$ 1,199,000	(42,000)	178,000
Warrants term						7 years
2012 Loan Agreement | Series D Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares													207,177
2013 Loan Agreement | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Change in fair value of preferred stock warrant liabilities										$ 217,000	$ 12,000	$ 19,000
Warrant exercise period										Oct. 26, 2016
Issuance of common stock upon exercise of warrants, Shares	13,414
Fair value warrants recorded as debt discount				$ 72,000
Fair value assumptions, discount rate				22.00%
2013 Loan Agreement | Series D Preferred Stock
Class Of Warrant Or Right [Line Items]
Warrants issued to purchase shares				18,474
Exercise price of warrants				$ 7.31
2013 Loan Agreement | Series D Preferred Stock | Warrant [Member]
Class Of Warrant Or Right [Line Items]
Warrants expiry period										Apr. 30, 2023