Warrants - Outstanding Warrants To Purchase Common Stock Warrants (Parenthetical) (Detail) - $ / shares		3 Months Ended	12 Months Ended
	Jul. 01, 2017	Mar. 31, 2018	Dec. 31, 2017	Oct. 10, 2017	Jul. 03, 2017	Jul. 02, 2017	Mar. 15, 2017	Sep. 26, 2016	Sep. 25, 2016
JGB Debt [Member]
Class Of Warrant Or Right [Line Items]
Shares issued upon conversion	1,022,544	6,415,039	6,415,039
Common Stock [Member]
Class Of Warrant Or Right [Line Items]
Warrants issued		3,633,565
Common Stock [Member] | JGB Debt [Member]
Class Of Warrant Or Right [Line Items]
Warrants, issued date		Mar. 15, 2017
Common Stock [Member] | Private Placement [Member] | Accredited Investors [Member]
Class Of Warrant Or Right [Line Items]
Warrants, issued date		Apr. 14, 2016
Exercise Price								$ 4.00	$ 4.98
Common Stock [Member] | Private Placement [Member] | Placement Agents [Member]
Class Of Warrant Or Right [Line Items]
Warrants, issued date		Apr. 14, 2016
Common Stock [Member] | Subsequent Financing [Member]
Class Of Warrant Or Right [Line Items]
Warrants, issued date		Jun. 15, 2016
Common Stock [Member] | Conditional Share Purchase Agreement [Member] | JGB Debt [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price					$ 1.12		$ 5.00
Shares issued upon conversion	1,022,544
Warrants issued							1,250,000
Common Stock [Member] | Conditional Share Purchase Agreement [Member] | Accredited Investors [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price					1.12	$ 4.00
Shares issued upon conversion	1,022,544
Common Stock [Member] | Conditional Share Purchase Agreement [Member] | Placement Agents [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price					1.12	$ 3.99
Shares issued upon conversion	1,022,544
Common Stock [Member] | Conditional Share Purchase Agreement [Member] | Former Majority Shareholders [Member] | JGB Debt [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price					$ 4.82
Warrants issued					1,296,679
Common Stock [Member] | Subsequent Private Placement [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price								$ 4.00	$ 4.98
Common Stock [Member] | 2017 Public Offering [Member] | JGB Debt [Member]
Class Of Warrant Or Right [Line Items]
Exercise Price				$ 4.67	$ 4.82
Warrants issued		1,296,679		1,338,326