Equity Transactions - Schedule of Reconciliation of Warrant Liability, Additional Paid-in Capital, Accumulated Defecit and Change in Fair Value of Warrant Liability on Balance Sheets (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Class Of Stock [Line Items]
Related-party notes payable, net of discount & issuance costs of $0 (2017) and $619 (2016)				$ 1,295
Notes payable, net of discount & issuance costs of $508 (2017) and $619 (2016)	$ 1,492			1,295
Accumulated comprehensive deficit	$ (232,773)			(226,228)
ASU 2017-11 [Member]
Class Of Stock [Line Items]
Related-party notes payable, net of discount & issuance costs of $0 (2017) and $619 (2016)		$ 1,425	$ 1,360	1,295	$ 1,242
Notes payable, net of discount & issuance costs of $508 (2017) and $619 (2016)		1,425	1,360	1,295	1,242
Additional paid-in capital		232,046	229,650	229,274	228,926
Accumulated comprehensive deficit		(231,063)	(229,108)	(226,228)	(222,503)
ASU 2017-11 [Member] | Change in Valuation of Notes Payable [Member]
Class Of Stock [Line Items]
Related-party notes payable, net of discount & issuance costs of $0 (2017) and $619 (2016)		267	298	328	359
Notes payable, net of discount & issuance costs of $508 (2017) and $619 (2016)		267	298	328	359
Additional paid-in capital		(534)	(596)	(656)	(718)
ASU 2017-11 [Member] | Reclassification of Warrant Liability [Member]
Class Of Stock [Line Items]
Warrant liability		(1,063)	(502)	(1,210)	(1,761)
Additional paid-in capital		1,063	502	1,210	1,761
ASU 2017-11 [Member] | Change in Fair Value of Warrant Liability [Member]
Class Of Stock [Line Items]
Additional paid-in capital		1,060	1,618	910	335
Accumulated comprehensive deficit		(1,060)	(1,618)	(910)	(335)
ASU 2017-11 [Member] | Change in Interest (Expense) Income Net [Member]
Class Of Stock [Line Items]
Additional paid-in capital		(200)	(139)	(79)	(17)
Accumulated comprehensive deficit		200	139	79	17
ASU 2017-11 [Member] | Previously Reported [Member]
Class Of Stock [Line Items]
Related-party notes payable, net of discount & issuance costs of $0 (2017) and $619 (2016)		1,158	1,062	967	883
Notes payable, net of discount & issuance costs of $508 (2017) and $619 (2016)		1,158	1,062	967	883
Warrant liability		1,063	502	1,210	1,761
Additional paid-in capital		230,657	228,265	227,889	227,565
Accumulated comprehensive deficit		$ (230,203)	$ (227,629)	$ (225,397)	$ (222,185)