Shareholders' Equity - Additional Information (Detail) $ in Thousands	6 Months Ended	9 Months Ended
	Jun. 30, 2017 USD ($) shares	Sep. 30, 2017 USD ($) shares	Dec. 31, 2016 shares
Class of Stock [Line Items]
Preferred stock, redemption date		Jun. 30, 2017
Series B Convertible Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding	0	0	130
Each share of preferred stock converted into common stock	2.78
Preferred shares converted into common stock, shares	361
Series C Preferred Stock [Member]
Class of Stock [Line Items]
Preferred stock, shares outstanding	0	0	550
Payment for redemption of preferred stock | $	$ 100
Amount recorded in excess of carrying value over redemption value | $		$ 459