Subsequent Events - Additional Information (Detail)		1 Months Ended	3 Months Ended		12 Months Ended
	Feb. 02, 2018 shares	Jan. 31, 2018 Fund shares	Jun. 30, 2016 shares	Mar. 31, 2016 shares	Dec. 31, 2017 shares	Dec. 31, 2016 shares
Subsequent Event [Member]
Subsequent Event [Line Items]
Number of funds | Fund		1
Board of Directors [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Shares issued during period (in shares)	47,766
Common Stock [Member]
Subsequent Event [Line Items]
Number of shares issued upon conversion			60,000	180,000	200,000	1,641,800
Common Stock [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of shares issued upon conversion		200,000
Series B Convertible Preferred Stock [Member]
Subsequent Event [Line Items]
Number of shares converted					1,000	8,209
Series B Convertible Preferred Stock [Member] | Subsequent Event [Member]
Subsequent Event [Line Items]
Number of shares converted		1,000