Secured Convertible Notes and Related Common Stock Purchase Warrants - Additional Information (Details) - USD ($) $ / shares in Units, shares in Millions		1 Months Ended				3 Months Ended		9 Months Ended
	Oct. 06, 2018	Sep. 30, 2018	Aug. 31, 2018	Jul. 31, 2018	Jun. 30, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Debt Instrument [Line Items]
Debt instrument, principal face amount		$ 9,400,000				$ 9,400,000		$ 9,400,000
Debt discount on senior notes		6,600,000				6,600,000		6,600,000
Notes payable maturity amount		$ 2,800,000				$ 2,800,000		$ 2,800,000
Exercise price of warrants		$ 2.85				$ 2.85		$ 2.85		$ 13,942.79
Loss on issuance of financial instrument						$ 0	$ 0	$ 2,826,000	$ 0
Fair value of warrants being reclassified from liability to equity						4,210,000
Loss on debt extinguishment						$ 0	$ 0	$ 0	$ (9,613,000)
Subsequent Event [Member]
Debt Instrument [Line Items]
Repayments of outstanding notes	$ 4,900,000
Maximum [Member]
Debt Instrument [Line Items]
Exercise price of warrants		19,712,000				$ 19,712,000		$ 19,712,000		19,712,000
Minimum [Member]
Debt Instrument [Line Items]
Exercise price of warrants		$ 0.01				$ 0.01		$ 0.01		$ 1,225
Third Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Exercise price of warrants			$ 1.75
June 2018 Series D Warrants [Member] | Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt discount on senior notes					$ 2,300,000
Shares issuable upon warrants exercised					1.1
Exercise price of warrants					$ 4.00
Loss on issuance of financial instrument					$ 2,800,000
Warrants term					5 years
June 2018 Pre-Funded Series D Warrants [Member]
Debt Instrument [Line Items]
Shares issuable upon warrants exercised			22.2
Warrants exercisable period				Jul. 20, 2018
Fair value of warrants being reclassified from liability to equity				$ 4,200,000
June 2018 Pre-Funded Series D Warrants [Member] | Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Shares issuable upon warrants exercised					13.0
Exercise price of warrants					$ 0.01
Buy back of warrants, description								The Company was initially able to buy back each June 2018 Pre-Funded Series D Warrant on its date of initial exercisability so long as the Company was not in default and the applicable installment payment for each month had been paid when due.
Warrants term					5 years
Warrants exercisable, description								June 2018 Pre-Funded Series D Warrants have a five-year term from initial exercisability which was to begin on the fifth day of each month commencing December 5, 2018, through December 5, 2019, for each of Warrant D-1-201 through 213 respectively.
Warrants exercisable, start date					Dec. 05, 2018
Warrants exercisable, end date					Dec. 05, 2019
July 2018 Pre-Funded Series D Warrants [Member]
Debt Instrument [Line Items]
Shares issuable upon warrants exercised			15.8
July 2018 Pre-Funded Series D Warrants [Member] | Second Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Shares issuable upon warrants exercised				9.2
Exercise price of warrants				$ 0.01
July 2018 Series D Warrant [Member] | Second Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt discount on senior notes				$ 1,400,000
Shares issuable upon warrants exercised				0.8
Exercise price of warrants				$ 4.00
Debt financing costs				$ 200,000
August 2018 Pre-Funded Series D Warrants [Member] | Third Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Shares issuable upon warrants exercised			23.8
Exercise price of warrants			$ 0.01
August 2018 Series D Warrant [Member] | Third Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt discount on senior notes			$ 2,100,000
Shares issuable upon warrants exercised			2.0
Exercise price of warrants			$ 1.75
Debt financing costs			$ 100,000
June Two Thousand Eighteen and July Two Thousand Eighteen Notes [Member]
Debt Instrument [Line Items]
Debt instrument, conversion price			$ 1.75
Percentage of subsequent financings used to repayment of notes payable			50.00%
Minimum percentage of change in cash flows			10.00%
Loss on debt extinguishment			$ 1,100,000
July 2018 Pre-Funded Series D Warrants [Member] | Fourth Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Shares issuable upon warrants exercised		3.1				3.1		3.1
Exercise price of warrants		$ 0.01				$ 0.01		$ 0.01
September 2018 Series D Warrant [Member] | Fourth Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt discount on senior notes		$ 400,000				$ 400,000		$ 400,000
Shares issuable upon warrants exercised		0.3				0.3		0.3
Exercise price of warrants		$ 1.75				$ 1.75		$ 1.75
June 2018 Convertible Note [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount		$ 3,400,000				$ 3,400,000		$ 3,400,000
Debt discount on senior notes		$ 1,500,000				$ 1,500,000		$ 1,500,000
Interest rate		8.00%				8.00%		8.00%
Notes payable maturity amount		$ 1,900,000				$ 1,900,000		$ 1,900,000
Debt instrument, conversion price		$ 1.75				$ 1.75		$ 1.75
June 2018 Convertible Note [Member] | Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Interest rate					8.00%
Notes payable terms								The June 2018 Notes bear 8% interest payable upon maturity. Of the $3.3 million in issued June 2018 Notes, $2.5 million matures in six months; the balance of $0.8 million is payable in twelve installments beginning seven months after the original issuance date.
Debt instrument, conversion price					$ 3.00
Maximum required market price of common shares, to settle notes payable in cash					$ 3.00
June 2018 Convertible Note [Member] | Securities Purchase Agreement [Member] | Matures in Six Months [Member]
Debt Instrument [Line Items]
Notes payable maturity amount					$ 2,500,000
June 2018 Convertible Note [Member] | Securities Purchase Agreement [Member] | Payable in Twelve Installments Beginning Seven Months After Original Issuance Date [Member]
Debt Instrument [Line Items]
Notes payable maturity amount					800,000
June 2018 Convertible Note [Member] | June 2018 Series D Warrants [Member] | Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount					3,300,000
Proceeds from issuance of notes and warrants					2,400,000
Debt discount on senior notes					1,100,000
June 2018 Convertible Note [Member] | June 2018 Pre-Funded Series D Warrants [Member] | Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount					$ 200,000
July 2018 Convertible Note [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount		$ 2,200,000				$ 2,200,000		$ 2,200,000
Debt discount on senior notes		$ 1,700,000				$ 1,700,000		$ 1,700,000
Interest rate		8.00%				8.00%		8.00%
Notes payable maturity amount		$ 500,000				$ 500,000		$ 500,000
Debt instrument, conversion price		$ 1.75				$ 1.75		$ 1.75
July 2018 Convertible Note [Member] | Second Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount				2,200,000
Proceeds from issuance of notes and warrants				1,600,000
Debt discount on senior notes				700,000
Notes payable terms								Of the $2.2 million in issued July 2018 Notes, $1.6 million matures in six months; the balance of $0.6 million is payable in twelve installments beginning seven months after the original issuance date.
July 2018 Convertible Note [Member] | Second Securities Purchase Agreement [Member] | Matures in Six Months [Member]
Debt Instrument [Line Items]
Notes payable maturity amount				1,600,000
July 2018 Convertible Note [Member] | Second Securities Purchase Agreement [Member] | Payable in Twelve Installments Beginning Seven Months After Original Issuance Date [Member]
Debt Instrument [Line Items]
Notes payable maturity amount				600,000
July 2018 Convertible Note [Member] | July 2018 Pre-Funded Series D Warrants [Member] | Second Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount				$ 100,000
August 2018 Convertible Note and Series D Warrant and Series D Pre-Funded Warrant [Member] | Third Securities Purchase Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount			6,000
August 2018 Convertible Note [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount		$ 3,300,000				$ 3,300,000		$ 3,300,000
Debt discount on senior notes		$ 2,900,000				$ 2,900,000		$ 2,900,000
Interest rate		8.00%				8.00%		8.00%
Notes payable maturity amount		$ 400,000				$ 400,000		$ 400,000
Debt instrument, conversion price		$ 1.75				$ 1.75		$ 1.75
August 2018 Convertible Note [Member] | Third Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount			3,300,000
Proceeds from issuance of notes and warrants			2,500,000
Debt discount on senior notes			$ 1,100,000
Interest rate			8.00%
Notes payable terms								Of the $3.3 million in issued August 2018 Notes, $2.5 million matures in six months; the balance of $0.8 million is payable in twelve installments beginning seven months after the original issuance date.
August 2018 Convertible Note [Member] | Third Securities Purchase Agreement [Member] | Matures in Six Months [Member]
Debt Instrument [Line Items]
Notes payable maturity amount			$ 2,500,000
August 2018 Convertible Note [Member] | Third Securities Purchase Agreement [Member] | Payable in Twelve Installments Beginning Seven Months After Original Issuance Date [Member]
Debt Instrument [Line Items]
Notes payable maturity amount			800,000
August 2018 Convertible Note [Member] | August 2018 Pre-Funded Series D Warrants [Member] | Third Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount			$ 200,000
September 2018 Convertible Note [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount		$ 500,000				$ 500,000		$ 500,000
Debt discount on senior notes		$ 500,000				$ 500,000		$ 500,000
Interest rate		8.00%				8.00%		8.00%
Debt instrument, conversion price		$ 1.75				$ 1.75		$ 1.75
September 2018 Convertible Note [Member] | Fourth Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount		$ 500,000				$ 500,000		$ 500,000
Proceeds from issuance of notes and warrants		400,000
Debt discount on senior notes		$ 200,000				200,000		200,000
Notes payable terms		Of the $0.5 million in issued September 2018 Notes, $0.4 million matures in six months; the balance of $0.1 million is payable in twelve installments beginning seven months after the original issuance date.
September 2018 Convertible Note [Member] | Fourth Securities Purchase Agreement [Member] | Matures in Six Months [Member]
Debt Instrument [Line Items]
Notes payable maturity amount		$ 400,000				400,000		400,000
September 2018 Convertible Note [Member] | Fourth Securities Purchase Agreement [Member] | Payable in Twelve Installments Beginning Seven Months After Original Issuance Date [Member]
Debt Instrument [Line Items]
Notes payable maturity amount		100,000				100,000		100,000
September 2018 Convertible Note [Member] | July 2018 Pre-Funded Series D Warrants [Member] | Fourth Securities Purchase Agreement [Member]
Debt Instrument [Line Items]
Debt instrument, principal face amount		$ 30,000				$ 30,000		$ 30,000